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The Effect of Lottery Scratch Tickets and Donation

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The Effect ofLottery ScratchTickets andDonation Offers onResponse Fraction:A Study andMeta-Analysis

Terry Boyle1, Jane Heyworth2, Jenny Landrigan2,Robin Mina2, and Lin Fritschi1

AbstractMonetary incentives are the most effective way of increasing response topostal questionnaires; however, mailing currency is prohibited in manycountries. Hence, nonmonetary incentives, such as lottery scratch ticketsand donation offers, have been used. The effectiveness of different typesof nonmonetary incentives is unclear, however. Two randomized con-trolled studies and meta-analyses were conducted to investigate the effectof two types of nonmonetary incentives on response. In the first study, the

1 Western Australian Institute for Medical Research, The University of Western Australia,

Nedlands, Western Australia, Australia2 School of Population Health, Faculty of Medicine, Dentistry, and Health Sciences, The

University of Western Australia, Crawley, Western Australia, Australia

Corresponding Author:

Terry Boyle, Western Australian Institute for Medical Research, The University of Western

Australia, B Block, Hospital Avenue, Sir Charles Gairdner Hospital, Nedlands, Western

Australia 6009, Australia

Email: tboyle@waimr.uwa.edu.au

Field Methods24(1) 112-132

ª The Author(s) 2012Reprints and permission:

sagepub.com/journalsPermissions.navDOI: 10.1177/1525822X11424549

http://fm.sagepub.com

authors found that participants who received an unconditional lotteryscratch ticket at invitation were 24% more likely to take part, while in thesecond study, the authors found that unconditional lottery scratch ticketsand donation offers had a similar effect on response. The meta-analysesshow that unconditional lottery scratch tickets significantly increase thechance of response by 9%, conditional scratch tickets have no effect, anddonation offers cause a nonsignificant 4% increase in the chance ofresponse. Unconditional lottery scratch tickets provide a modest increasein the likelihood of response.

Keywordsepidemiologic methods, questionnaires, response rate, incentives

Unconditional monetary incentives have been found to be the most effective

way of increasing response fractions to postal questionnaires (Edwards et al.

2005; Edwards et al. 2009). Sending currency in the regular mail is prohibited

in Australia (Australia Post 2009) and many other countries (Royal Mail Group

2010); however, nonmonetary incentives, such as lottery scratch tickets and

donation offers, have been used. A recent meta-analysis found that nonmone-

tary incentives increase the odds of response by 15% (95% confidence interval

[CI]: [1.08, 1.22]; Edwards et al. 2009). However, as acknowledged by

Edwards et al. (2009), there was substantial heterogeneity among the studies

that investigated the effect of nonmonetary incentives, so it may not be appro-

priate to combine them. Combining these studies also makes it difficult to

determine what specific kinds of nonmonetary incentives are effective.

The studies that have investigated the effect of lottery scratch tickets on

response have generally had null findings (Finsen and Storeheier 2006;

Harris, Khoo, et al. 2008; Kalantar and Talley 1999; Koloski et al. 2001;

Ward et al. 1996; Wenemark et al. 2010; Whiteman et al. 2003), with only

one study showing a significant increase in the likelihood of response

(Robertson et al. 2005). Several studies have shown a borderline, but non-

significant, increase in response (Brennan et al. 1993; Kalantar and Talley

1999; Ward et al. 1996; Whiteman et al. 2003), which suggests that they

may have had insufficient power to detect a significant difference. The

published research about the effect of donation offers on response has

shown mixed results, with some studies showing no effect or a decrease

in response (Gattellari and Ward 2001; Gendall and Healey 2008; Hubbard

and Little 1988; Skinner et al. 1984), and others showing an increase in

response (Brennan et al. 1993; Deehan et al. 1997; Faria and Dickinson

Boyle et al. 113

1992; Furse and Stewart 1982; Gendall and Healey 2008; Robertson and

Bellenger 1978; Warriner and Goyder 1996). Overall, there is limited

research concerning the effectiveness of lottery scratch tickets and donation

offers.

We conducted two studies to investigate the effect of different types of

nonmonetary incentives on response fraction in the Western Australian

Bowel Health Study (WABOHS), a case–control study of the genetic and

environmental causes of colorectal cancer. The aims of the first study were

to determine whether (1) lottery scratch tickets given at the time of invita-

tion increase response fraction and (2) lottery scratch tickets given at the

same times as the study instruments increase the likelihood that participants

will complete and return them.

For the second study, we modified the incentive to be one of three: a lot-

tery scratch ticket, a donation to The Cancer Council Western Australia, and

a lottery scratch ticket plus a donation. We wanted to compare these incen-

tives as it was hypothesized that a donation to a cancer organization might

be more acceptable than a lottery ticket that could be perceived as having an

association with gambling. We also wanted to determine whether the com-

bination of a personal incentive (a lottery scratch ticket) and an altruistic

incentive (a charitable donation) increased response more than either of

these incentives alone. So, the aim of the second study was to (3) investigate

if a donation offer, or both a donation offer and a lottery scratch ticket,

increased response fraction more than a lottery scratch ticket alone.

We also performed a meta-analysis to determine whether lottery scratch

tickets or donation offers increase response to postal questionnaires.

Method

The two studies were part of a larger study, the WABOHS, the methodology

of which has been described elsewhere (Iacopetta et al. 2009). The

WABOHS was a case–control study of colorectal cancer that took place

between 2005 and 2007 in Western Australia. Cases studied involved indi-

viduals with colorectal cancer who were notified to the Western Australian

Cancer Registry. Age- and sex-matched controls were selected randomly

from the electoral roll of Western Australia. Registration on the electoral

roll is compulsory in Australia, and it is considered virtually complete.

Fifty-eight percent of eligible cases and 46% of eligible controls partici-

pated in the WABOHS.

Ethics approval for both substudies was obtained from the University

of Western Australia Human Research Ethics Committee and the

114 Field Methods 24(1)

Confidentiality of Health Information Committee within the Western

Australian Department of Health.

Study 1

In February 2007, 308 controls (aged between 40 and 79) were randomly

selected from the electoral roll and invited to participate in the WABOHS.

The participants received an invitation letter, an information sheet about the

study, a consent form, and a reply-paid envelope. Using block randomiza-

tion, the controls were allocated into one of two groups at the time of

invitation—Group B received a $2 lottery scratch ticket with their invita-

tion; Group A did not. Nonresponders were sent a reminder letter 3 weeks

after the initial invitation.

Participants who consented to take part in the WABOHS were then sent

a study pack that consisted of two questionnaires and a DNA self-extraction

kit. These participants were randomized further into three groups when sent

their study packs, ignoring their initial allocation to Group A or B (see

Figure 1). Group 0 did not get a lottery scratch ticket, Group 1 received a

$2 lottery scratch ticket, and Group 2 was promised a $2 lottery scratch

ticket on return of their completed study pack. Nonresponders in all three

groups were sent a reminder card after 3 weeks and a replacement study

pack after 5 weeks. The consent forms of seven consenting participants

were received several months after the first study had concluded—these

participants were included in the overall consent and response fractions

(Table 1) but were not included in the second part of the study (Table 2).

Study 2

In June 2007, an additional 300 controls (aged between 40 and 79) were

randomly selected from the electoral roll and invited to participate in the

WABOHS. In this study, the participants were allocated (using block

randomization) into one of the three groups at the time of invitation

(Figure 2). Group X received a $2 lottery scratch ticket with their invitation,

Group Y were told that $2 would be donated to The Cancer Council West-

ern Australia if they returned their consent form (regardless of whether or

not they agreed to take part in the WABOHS), and Group Z received both

a $2 lottery scratch ticket and the donation offer. Nonresponders in all three

groups were sent a reminder letter 3 weeks after the initial invitation. Con-

senting participants were sent a study pack to complete but did not receive

any incentives at the second stage. Participants who did not return their

Boyle et al. 115

308

part

icip

ants

ran

dom

ly

sele

cted

fro

m th

e el

ecto

ral r

oll

Gro

up A

: 154

par

ticip

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t inv

itatio

n w

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up B

: 154

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itatio

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ith

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eed

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udy

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etur

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et

3 pa

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ipan

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le1

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icip

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inel

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le

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gree

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pa

rtic

ipat

e la

te3

part

icip

ants

agr

eed

to

part

icip

ate

late

Figure 1. Design of study 1.

116 Field Methods 24(1)

study pack were sent a reminder card after 3 weeks and a replacement study

pack after 5 weeks.

Statistical Analysis

Consent fractions, response fractions, and risk ratios were generated using

the statistical package Stata 10.0 (StataCorp., College Station, TX). Consent

fraction refers to the percentage of all eligible invited participants who indi-

cated on their returned consent form that they were willing to take part in

the study. Response fraction refers to the percentage of all eligible invited

participants who returned a completed study pack. Risk ratios were gener-

ated using a modified Poisson regression approach (Zou 2004). Effect

Table 1. Response and Consent Fractions among Participants Receiving Either aLottery Scratch Ticket or No-Incentive at the Time of Invitation (N ¼ 304)

NumberResponding Percentage

RiskRatio 95% CI

Consent fraction before reminderGroup A. No incentive (n ¼ 151) 62 41.1 1.00 —Group B. Scratch ticket (n ¼ 153) 82 53.6 1.31 [1.02, 1.66]

Consent fraction after reminderGroup A 85 56.3 1.00 —Group B 96 62.7 1.11 [0.93, 1.34]

Consented and completed study pack (response fraction)Group A 70 46.4 1.00 —Group B 88 57.5 1.24 [1.00, 1.55]

Table 2. Study Pack Return among Groups that were Given, Promised, or NotGiven an Incentive with the Study Pack (N ¼ 174)

NumberResponding Percentage

RiskRatio 95% CI

Group 0. No incentive with studypack (n ¼ 58)

50 86.2 1.00 —

Group 1. Incentive with study pack(n ¼ 57)

49 86.0 1.00 [0.86, 1.16]

Group 2. Promised incentive onreceipt of completed study pack(n ¼ 59)

56 94.9 1.10 [0.98, 1.24]

Boyle et al. 117

300

part

icip

ants

ran

dom

ly

sele

cted

fro

m th

e el

ecto

ral r

oll

Gro

up X

: 100

part

icip

ants

sen

t in

vita

tion

wit

h $2

scr

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tick

etG

roup

Z: 1

00pa

rtic

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ent

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ith

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da

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onat

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: 100

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r

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50pa

rtic

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nt

3 pa

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ipan

ts

inel

igib

le

Figure 2. Design of study 2.

118 Field Methods 24(1)

modification by age, sex, or invitation incentive group (Study 1b) was

examined using postestimation Wald’s chi-square tests.

Meta-Analyses

A systematic search of Medline, PsychInfo, Cochrane Controlled Trials

Register, Embase, Institute for Scientific Information (ISI), Web of

Knowledge, Proquest 5000, and Scopus (to June 2010) was conducted

to identify studies that had investigated the effect of scratch lottery tick-

ets or donation offers on response. Only studies that compared the use

of lottery scratch tickets or donation offers with a no monetary or non-

monetary incentive control group were considered. Only studies that

involved postal surveys/questionnaires were included; studies that inves-

tigated the effect of these incentives on response to web-based question-

naires or telephone surveys were not considered. Studies from any

populations were considered, as long as they were published in English

in a peer-reviewed journal.

The following search strategy was used for lottery scratch ticket articles:

1. questionnair* or survey* or data collection

2. respon* or return*

3. lottery or instant or scratch*

4. ticket or card

5. 1 & 2 & 3 & 4

The following search strategy was used for donation offer articles:

1. questionnair* or survey* or data collection

2. respon* or return*

3. charit* and donat*

4. 1 & 2 & 3

The lottery scratch ticket search resulted in a total of 78 articles. Of these,

57 were not considered as they were not related to response to question-

naires. Of the remaining 21 articles, 13 were not included in the meta-

analysis as they did not involve lottery scratch tickets or did not have a

no-incentive control group. The donation offer search resulted in a total

of 156 articles. Of these, 147 were not considered as they were not related

to response to questionnaires. Of the remaining nine articles, two were not

included in the meta-analysis as they did not involve donation offers or did

Boyle et al. 119

not have a no-incentive control group. The recent Cochrane review con-

cerning the use of incentives in mailed and online questionnaires was also

searched (Edwards et al. 2009), resulting in one additional study for

the lottery scratch ticket meta-analysis and two additional studies for the

donation offer meta-analysis. A search of the reference lists of all the

eligible articles did not find any additional studies. Three further studies

were added to the donation offer meta-analysis during the review process

of this article.

In total, 9 studies (including the present study) were included in the lot-

tery scratch ticket meta-analysis, and 12 studies were included in the dona-

tion offer meta-analysis. The characteristics of these studies can be found in

Tables 3 and 4.

If a study had more than one incentive group level, these levels were

combined to produce a dichotomous result (i.e., incentive groups vs. no-

incentive groups). The outcome was the proportion of returned question-

naires after all mailings. As incentives given unconditionally have been

shown to have significantly greater effect on response than those given

conditionally (Edwards et al. 2009), studies that used conditional lottery

scratch tickets were analyzed separately than those that used unconditional

lottery scratch tickets.

Table 3. Response and Consent Fractions among Participants Receiving Eithera Lottery Scratch Ticket, a Donation Offer, or Both, at the Time of Invitation (N¼ 296)

NumberResponding Percentage

RiskRatio 95% CI

Consent fraction before reminderGroup X. Scratch ticket only

(n ¼ 100)37 37.0 1.00 —

Group Y. Donation only (n ¼ 97) 32 33.0 0.89 [0.61, 1.31]Group Z. Donation/scratch ticket

(n ¼ 99)39 39.4 1.06 [0.75, 1.52]

Consent fraction after reminderGroup X 45 45.0 1.00 —Group Y 47 48.5 1.08 [0.8, 1.45]Group Z 48 48.5 1.08 [0.8, 1.45]

Consented and completed study pack (response fraction)Group X 41 41.0 1.00 —Group Y 44 45.4 1.11 [0.8, 1.52]Group Z 41 41.4 1.01 [0.72, 1.41]

120 Field Methods 24(1)

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121

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122

The command metan in the statistical package Stata 10.0 (StataCorp,

College Station, TX) was used to conduct random-effects meta-analyses

(DerSimonian and Laird 1986).

Results

Study 1

Of the 308 controls invited in the first study, 4 were not contactable due to

incorrect addresses. Group A (no incentive) had a mean age of 62.1 years

(range ¼ 40–79 years) and Group B (lottery scratch ticket) had a mean age

of 62.5 years (range ¼ 42–79 years). The proportion of females in each

group was 38.4% and 37.9%, respectively. Of the eligible 304 controls,

181 (144 before the reminder letter and 37 after the reminder letter) con-

sented to take part in the WABOHS (consent fraction ¼ 59.5%), with

158 completing and returning their study pack (response fraction ¼52.0%). The reminder letter increased the consent fraction from 47.4% to

59.5%.

Participants who received a lottery scratch ticket with their invitation

(Group B) were 1.24 times (95% CI [1.00, 1.55]) more likely to take part

in the study than participants who did not receive an incentive (Table 1).

Participants who received a lottery scratch ticket with their invitation were

1.31 times (95% CI [1.02, 1.66]) more likely to consent to take part in the

study without needing a reminder than those who did not receive an incen-

tive. There was no significant difference in consent fractions between the

two groups following the reminder letter. There were no significant sex

or age differences in terms of the effect of the incentive.

There were no significant differences in the likelihood of participants

completing and returning their study pack between the three study pack

incentive groups (Table 2). The invitation incentive group did not signifi-

cantly modify the effect of the study pack incentive (the response fractions

of the six individual groups can be found in Table 5).

Study 2

Of the 300 controls invited in the second study, 4 were not contactable due

to incorrect addresses. Group X (lottery scratch ticket only) had a mean age

of 58.6 years (range ¼ 40–79 years), Group Y (donation only) had a mean

age of 59.7 years (range¼ 40–79 years), and Group Z (both incentives) had

a mean age of 58.0 (range ¼ 40–79 years). The proportion of females in

each group was 38%, 44.4%, and 41.2%, respectively. Of the eligible 296

Boyle et al. 123

controls, 140 (108 before the reminder letter and 32 after the reminder letter)

consented to take part in the WABOHS (consent fraction ¼ 47.3%), with

126 completing and returning their study pack (response fraction ¼ 42.6%).

The reminder letter increased the consent fraction from 36.5% to 47.3%.

The highest response fraction was seen in Group Y (donation only);

however, there were no significant differences in consent and response frac-

tions between the three different incentive groups (see Table 3). There were

no significant sex or age differences in terms of the effect of the incentive.

Meta-Analyses

The characteristics of the studies included in the meta-analyses can be

found in Tables 4 and 6. As shown in Figure 3, the results of the random-

effects meta-analyses show that lottery scratch tickets given uncondition-

ally significantly increase the likelihood of response by 9% (risk ratio

[RR] ¼ 1.09, 95% CI [1.02, 1.16]), compared with a no-incentive control

group. Lottery scratch tickets given conditionally appear to have no effect

on response (RR ¼ 0.97, 95% CI [0.91, 1.04]). There was no significant

Table 5. Study Pack Return among Groups that Were Given or Not Given anIncentive with the Invitation and Were then Given, Promised, or Not Given an Incen-tive with the Study Pack (N ¼ 174)

NumberResponding Percentage

RiskRatio 95% CI

Group A. No incentive with invitationGroup 0. No incentive with studypack (n ¼ 27)

20 74.1 1.00 —

Group 1. Incentive with studypack (n ¼ 25)

21 84.0 1.13 [0.86, 1.50]

Group 2. Promised incentive onreceipt of completed study pack(n ¼ 29)

28 96.6 1.30 [1.03, 1.65]

Group B. Incentive with invitationGroup 0. No incentive with studypack (n ¼ 31)

30 96.8 1.31 [1.04, 1.65]

Group 1. Incentive with studypack (n ¼ 32)

28 87.5 1.18 [0.91, 1.53]

Group 2. Promised incentive onreceipt of completed study pack(n ¼ 30)

28 93.3 1.26 [0.99, 1.61]

124 Field Methods 24(1)

Tab

le6.

Char

acte

rist

ics

ofth

eSt

udie

sIn

cluded

inth

eD

onat

ion

Offer

Met

a-A

nal

ysis

Firs

tA

uth

or,

Yea

rPar

tici

pan

ts,Lo

cation

Surv

eyT

opic

Ince

ntive

Gro

ups

(and

Num

ber

of

Par

tici

pan

ts)

Use

din

This

Anal

ysis

Qual

ity

ofA

lloca

-tion

Conce

alm

ent

Rober

tson

and

Bel

lenge

r1978

Res

iden

tsofD

enve

r,U

SAN

ot

spec

ified

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

150)

Uncl

eara

2.U

S$1

contr

ibution

toch

arity

(N¼

150)

Furs

ean

dSt

ewar

t1982

Mic

row

ave

ove

now

ner

s,U

SAN

ot

spec

ified

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

100)

Uncl

eara

2.U

S$1

contr

ibution

toch

arity

(N¼

100)

Skin

ner

etal

.1984

Mar

keting

pro

fess

ors

inC

anad

aA

nin

troduct

ory

mar

keting

textb

ook

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

60)

Uncl

eara

2.C

A$1

contr

ibution

toch

arity

(N¼

60)

Hubbar

dan

dLi

ttle

1988

Res

iden

tsofa

mid

wes

tern

met

ropolit

anar

ea,U

SASa

tisf

action

with

finan

cial

serv

ices

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

400)

Uncl

eara

2.U

S$1

contr

ibution

toch

arity

(N¼

400)

Fari

aan

dD

icki

nso

n1992

Busi

nes

scu

stom

ers

ofa

maj

or

man

ufa

cture

r,C

anad

aN

ot

spec

ified

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

500)

Adeq

uat

ea

2.C

A$2

contr

ibution

toch

arity

(N¼

1,0

00)

Bre

nnan

etal

.1993

Res

iden

tsofN

ewZ

eala

nd

Att

itudes

tow

ard

soci

alin

equal

ity

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

452)

Uncl

eara

2.N

Z$1

contr

ibution

toch

arity

(N¼

478)

(con

tinue

d)

125

Tab

le6

(co

nti

nu

ed

)

Firs

tA

uth

or,

Yea

rPar

tici

pan

ts,Lo

cation

Surv

eyT

opic

Ince

ntive

Gro

ups

(and

Num

ber

of

Par

tici

pan

ts)

Use

din

This

Anal

ysis

Qual

ity

ofA

lloca

-tion

Conce

alm

ent

War

riner

and

Goyd

er1996

Res

iden

tsofth

eG

rand

Riv

erW

ater

shed

regi

on,O

nta

rio,

Can

ada

Envi

ronm

enta

lis

sues

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

110)

Inad

equat

ea

2.C

A$2,$5

or

$10

contr

ibution

toch

arity

(N¼

139)

Dee

han

etal

.1997

Gen

eral

pra

ctitio

ner

sin

Engl

and

and

Wal

esW

ork

with

alco

hol-

abusi

ng

pat

ients

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

1,1

88)

Uncl

eara

2.G

B£5

or

£10

contr

ibution

toch

arity

(N¼

1,1

85)

Gat

tella

rian

dW

ard

2001

Act

ive

Fello

ws

ofth

eR

oya

lA

ust

rala

sian

Colle

geof

Surg

eons

Clin

ical

pra

ctic

egu

idel

ines

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

111)

Adeq

uat

ea

2.A

U$10

contr

ibution

toth

eR

AC

S(N¼

108)

Gen

dal

lan

dH

eale

y2008

Res

iden

tsofN

ewZ

eala

nd

Imm

igra

tion

inN

ewZ

eala

nd

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

200)

Uncl

ear

2.N

Z$1

contr

ibution

toch

arity

(N¼

200)

Gen

dal

lan

dH

eale

y2008

Res

iden

tsofN

ewZ

eala

nd

Adve

rtis

ing

Reg

ula

tion

1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

500)

Uncl

ear

2.N

Z$1

contr

ibution

toch

arity

(N¼

500)

Gen

dal

lan

dH

eale

y2010

Res

iden

tsofN

ewZ

eala

nd

Rel

igio

n1.N

om

onet

ary

or

nonm

onet

ary

ince

ntive

(N¼

406)

Uncl

ear

2.N

Z$1,$2

or

$5

contr

ibution

toch

arity

(N¼

1,5

47)

Not

e:a Fr

om

Edw

ards

etal

.(2

009).

126

heterogeneity among the studies that examined the effect of lottery scratch

tickets given unconditioanlly (p ¼ .128) or conditionally (p ¼ .555).

Compared with a no-incentive control group, donation offers may

increase the likelihood of response by 4% (RR ¼ 1.04, 95% CI [0.96,

1.14]), although this result was not statistically significant (Figure 3). There

was significant heterogeneity among the studies that examined the effect of

donation offers on response (p < .001). Stratifying the studies by question-

naire topic (commercial or social/health) and study location (Australasia,

North America, or Europe) did not account for the significant heterogeneity,

nor did it reveal any meaningful differences between the effect sizes.

A sensitivity analysis, in which each study was omitted from the

meta-analysis one at a time, showed no notable impact of any study on the

effect size.

Figure 3. Meta-analyses and forest plot of studies that have investigated the effectof lottery scratch tickets or donation offers on response to mailed questionnaires.

Boyle et al. 127

Discussion

The results of the first study and the meta-analysis suggest that lottery

scratch tickets, when given unconditionally, provide a modest increase in

response to mailed questionnaires. In the first study, participants who

received a lottery scratch ticket with their invitation were 1.24 times more

likely to take part in the study than participants who did not receive an

incentive, although this increase just failed to reach statistical significance.

The results of the meta-analysis show that, compared with a no-incentive

control group, lottery scratch tickets given unconditionally increase the

likelihood of a participant responding by 9%. The meta-analysis also sug-

gests that lottery scratch tickets given conditionally do not appear to

increase response, a finding that confirms incentives given unconditionally

are more effective than those given conditionally (Edwards et al. 2009).

In our first study, lottery scratch tickets significantly increased the likeli-

hood of participants consenting before the reminder letter. This finding is con-

sistent with the results of other studies (Kalantar and Talley 1999; Robertson

et al. 2005), suggesting that if researchers are not planning to follow up non-

responders, using a lottery scratch ticket may be an effective method to

increase response. The increased response to the first mailing also reduces the

costs and resources associated with the sending of reminders, which offsets the

cost of the lottery scratch tickets to a certain extent (Kalantar and Talley 1999).

It is important to note, however, that follow-up contact has been shown to be a

very effective method of increasing response fraction (Edwards et al. 2009),

and the findings of this study—in which a reminder letter increased the

response fraction from 47.4% to 59.5% in the first study and from 36.5% to

47.3% in the second study—support this.

The results of the first study also indicate that giving or promising a lot-

tery scratch ticket with the study instruments does not significantly increase

the likelihood that participants will complete and return them.

The results of the second study suggest that lottery scratch tickets and

donation offers have a similar overall effect on consent and response frac-

tions. This suggests that incentives that have an altruistic benefit (i.e., dona-

tion offers) have a similar effect to incentives that may lead to personal

benefit (i.e., lottery scratch tickets). However, in the meta-analyses, we

found that lottery scratch tickets may have a greater effect on response than

donation offers. Lottery scratch tickets given unconditionally increase the

likelihood of response by 9%, while donation offers increase the chance

of response by 4%. The 4% increase was not statistically significant, and

there was significant heterogeneity among the studies that have investigated

128 Field Methods 24(1)

the effect of donation offers on response, so the effect of donation offers on

response remains unclear.

The fact that the two studies were both done within a larger study (the

WABOHS) led to some limitations. The number of participants in both the

first and the second studies, particularly in the final three groups in the first

study, limited our ability to draw conclusions; however, the total sample

size was constrained by the number of participants invited to take part in

the WABOHS at that time. A no-incentive control group in the second study

may have made the effect of different types of nonmonetary incentives

more clear. The generalizability of the results of the two studies may be lim-

ited, as both were conducted with quite homogeneous samples in a health

research setting. Likewise, all the studies in the lottery scratch tickets

meta-analysis were conducted within a health or social research setting,

so the results may not be generalizable to other research settings (e.g., mar-

ket research).

Despite using several techniques that have been shown to increase

response fraction—including personalized invitation letters, university

sponsorship, supplying a reply-paid envelope, reminder letters, promising

to supply the results of the study, and using a nonmonetary incentive, and

reminders (Edwards et al. 2009)—the final response fraction among con-

trols in the entire WABOHS was a modest 46%. Given that the nonmone-

tary incentives used in this study appear to result in only a small increase

in the likelihood of response, it is important that the effect of other types of

incentives on response is investigated. With response fractions in epide-

miological studies declining (Morton et al. 2006), and considering that

even small amounts of nonresponse bias can lead to inflation or attenua-

tion of the true effect (Harris, Levy, et al. 2008), increasing response is an

important issue.

Acknowledgments

Many thanks to Cassandra Clayforth, Clare Tran, Beatriz Cuesta-Briand,

and Kieran McCaul for their contributions to the two studies. The authors

also thank the four reviewers of this article for their thoughtful and con-

structive comments. Lin Fritschi is supported by an NHMRC Fellowship.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the

research, authorship, and/or publication of this article.

Boyle et al. 129

Funding

The author(s) disclosed receipt of the following financial support for the

research, authorship and/or publication of this article: The Western Austra-

lian Bowel Health Study was funded by the National Health and Medical

Research Council (Grant Number 353568). The funding source had no

involvement in either of these studies.

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