Research Revision Topics

8/7/2019 Research Revision Topics

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Before-and-after design

Have a pretest and posttest but nocomparison group,subjects exposed to

treatment serve at an earlier time as their owncontrols

Absence of a comparison/control group


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Validity in experiments

Internal validity-causalGeneralizability-able to apply the findings to some

clearly defined larger population

Cross-population generalizability-generalize acrosssubgroups and to oher populations and settings


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Unrepresentative sample

Some characteristics are

overrepresented orunderrepresented


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Types of experimental designs

Experimental design

Quasi-experimental designNonexperimental design


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Two types of before-and afterdesigns

1.Time series designs-consisting of manypretests and posttest observations of same

group(30 or more) 2. repeated measure paneldesign-several pretests and post test of samegroup


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Two major types of quasi-experimental designs

1. Nonequivalent control group

design 2. Before-and-after design


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Two major types of quasi-experimental designs

1. Nonequivalent control group designs-norandom assignment to groups 2. before and

after design- has pretest and posttest nocomparison group


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Two functions of Probes

1. They motivate the respondent to elaborateor clarify an answer or to explain reasons 2.

they help focus the conversation on thespecific topic of the interview


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True Experiments must haveat least 3 things

1. An experimental and control group 2.variation in the independent variable before

assessment of change in the dependentvariable(treatment) 3. random assignment totwo groups


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Time Series Design

Research designs in which pretests and posttests areare available on a number of occassions before and

after the introduction of independent variable at least 3

sets of measures before and afterO1 O2 O3 X O4 O5 O6


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The Principles of Interviewing

1. Respondents need to feel that their interaction withthe interviewer will be pleasant and satisfying 2. the

respondents need to see the study as being worthwhile

3. barriers to he interview in the respondents mindneed to be overcome-misperceptions and suspicion ofrespondent adddressed


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The Personal Interview

Regarded as a face-to-face interpersonal rolesituation in which an interviewer asks

respondents questions to obtains answersrelated to research hypothesis


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The Classic ExperimentalDesign

Experimental group, control group

randomization pretest posttest


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Telephone survey

Or telephone interview

A semipersonal method of collectinginformation,convenient and cost saving

method


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Telephone survey

Random digit dialing-draw a random sample of telephonenumbers, requires the identification of all working telephoneexchanges in the target area.a potential telephone number is

created by randomly selecting an exchange and thenappending a random number between 0001 and

9999.Additional numbers are created by repeating these twosteps.Nonresidential and nonworking numbers are excluded


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Target population

A set of elements larger than ordifferent from the population sampled

and to which the researcher would liketo generalize study findings.


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Systematic sampling

Select every kth element in a population,where k isdetermined by dividing the population sixe by the

desired sample size. Select a random number between

0 and k and picking that element in thepopulation,systematically pick every kth element


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Survey Sampling

Sampling designed to produce

information about particular

characteristics of a finite population.


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Survey research methods

Provide ways to describe the variablesin populations and to test the

relationships among variables inpopulations.


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Survey research is popularbecause of 3 features

1. versatility-cover a range of topics,computertechnology has made surveys more versatile 2.

efficiency-many variables can be measured without

greatly increasing the time or cost 3.generalizability-lend themselves to probability sampling from largepopulations.


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Survey Research Center U ofMich pointers

1. Tell respondent who you are and whom yourepresent 2. Tell what you are doing to stimulate

interest 3. tell how he or she was chosen 4. adapt

approach to situation5. try to create relatioship ofconfidence and understanding-rapport 5. initialinstructions should be brief


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Survey Research

Involves the collection of information

from a sample of individuals through

their response to questions.


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Stratified samples

Done by dividing the population intogroups(strata) that are homogeneous

on one or more traits,then samplingfrom each of these groups


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Stratified Proportionatesample

The number of elements selected from each stratum isproportional to that stratums representation in the

population

The same number of sampling units from each stratumor a uniform sampling fraction (n/N)


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Stratified Disproportionatesample

Chosen to yield numbers in a stratum to allow intensiveanalysis of that particular stratum

Variable sampling fractions,total number in each

stratum is different,population parameters have to beweighted by the number of each stratum


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Standard error

Allows the researcher to determine the probability thata given sample estimate is close to the actual

population value.

S.E.=standard error,the distribution of all samplesabout the mean of the samples is S.E.Calculate

standard deviation and estimate the S. E.


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Simple random sampling

Numbering all population elements,thenselecting enough random numbers to

complete a sample of the desired size.It issimple but inconvenient with largepopulations


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Sampling Theory

Major objective is to provide accurateestimates of unknown parameters in

population from sample statisticsPopulation=parameter sample=statistic


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Sampling Error -contd

The larger the sampling error,the

less representative the sample.


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Sampling Error

Any difference between the

characteristics of a sample andthe characteristics of a population


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Sampling distribution

When an infinite number of independentlyselected sample values such as the meansare placed in a distribution,the distribution is

called the sampling distributionIts standard deviation is the standard error


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Sample generalizability

Refers to the ability to generalize from

a sample ,or subset of a larger

population to that population itself.


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Sample

A subset of a population that is used to

study the population as a whole.

Subset=sample


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Research designs are

Cross-sectional design a study in which dataare collected at only one point in time or

longitudinal design-research in which data arecollected at two or more points in time,datacan be ordered in time


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Research Design

Is a blueprint for research

A plan for collecting,analyzing and interpreting datathat allows the investigator to make causal inferences

Process for deciding what aspects well observe,ofwhom,for what purpose


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Representative sample

A sample that looks like thepopulation from which it was selected

in all respects that are potentiallyrelevant to the study.


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Random selection procedures

Ensure that every sampling unit of thepopulation has an equal and known

probability of being included in the sample,theprobability is n/N n=sample, N=population


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Random Selection

Each element has an equal chance of

selection independent of any other

event in the selection process


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Quasi-experimental design

Comparison group comparable toexperimental group in critical ways

Subjects are not randomly assigned tothe groups


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Quasi-experimental design

Subjects are not randomly

assigned to to the experimentaland control or comparison group


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Quasi experiments differ fromexperiments in their lack of

Randomization is a defining characteristic ofexperiments

In time series designs the moremeasurements of the dependent variable youet, the stronger your design


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Purposive or judgmentalsample

Select a sample that, in their

subjective judgment,isrepresentative of the population


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Procedures of Control

1. Randomization or random assignment-removes bias fromthe assignment process by relying on chance-flipping coin or

random number table assures that case has an equalprobability of being assigned to either group 2. matching- or

pairwise matching,for each case in experimental group,another one with identical characteristics is selected for the

control group


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Probing

The technique used by the

interviewer to stimulate discussionand obtain more information


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Probability vs. NonprobabilitySampling

Probability sample allows estimates topopulation from sample Nonprobability

sample-list of sample population isunavailable-e;g, illegal residents, drug addicts


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Probability Sample Designs

1. random sample 2. systematicsamples 3. stratified samples-

proportionate, disproportionate 4.cluster samples 5. multistage samples


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pretests

Measures the dependent variables prior tothe experimental intervention,they provide a

direct measure of how much the experimentaland comparison groups changed overtime,tests effects of intervention


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PPS-probability proportionateto size

Type of multistage cluster sample inwhich clusters are selected,not with

equal probabilities(EPSEM) but withprobabilities proportionate to their sizes


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posttest

Measurement of the outcome in

both groups after the experimentalgroup has received the treatment


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Post test Only Control GroupDesign

Posttest

R X 01

R 02


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Population-finite or infinite

Finite population-contains a countablenumber of sampling units

Infinite population-consists of an endlessnumber of sampling units,an unlimited

number of coin tosses


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Population

The entire set of individuals or otherentities to which study findings are to

be generalizedWhole=population


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Omnibus survey

A survey that covers a range of topics ofinterest to different social scientists,example

General Social Survey GSS of the NationalOpinion Research Center at the University ofChicago


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Nonschedule-structuredInterview

Focused and structured but the respondentsare given much liberty in expressing their

definition of a situation that is presented tothem.Permits the researcher to obtain detailsof personal reactions,specific emotions, etc


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Nonscheduled Interview

Least structured form,or nondirective.Noprespecified set ofquestions is used,nor are the questions asked in a specific

order.No schedule is used. With little or no directon from theinteriewer, respondents are encouraged to relate their

experiences,to reveal opinion and attitude as they see fit.Interviewer has freedom to probe and raise questions


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Nonprobability SampleDesigns

1. Convenience samples 2. purposiveor judgmental samples 3. snowball

samples 4.quota samples


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Nonexperimental designs

1. Ex post facto(after the fact) controlgroup design-comparison group

selected after treatment occurred 2.one shot case study(cross-sectional


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Nonequivalent control group

Experimental and control/comparison groupdesignated before treatment occurs,not

created by random assignmentIndividual or aggregate matching used


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Mundane realism

Degree to which experiment is

superficially similar to everyday

situations


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Internal validity in experimentsfive threats

1. Selection bias-differential attrition 2. endogeneous change regression toward mean extreme scores on dep var become lessextreme on post test,testing, maturation-age,experience 3. history

effects-effect of external events-disasters 4. contamination

compensatory rivalry(John Henry effect)control group increase effortbecause denied advantage, demoralization-control group performworse because left out, Hawthorne effect-treatment group change on

dependent variable because participation make feel special


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Four types of errors in surveyresearch

1. Poor measurement-respondent satisficing whendont put forth effort 2. nonresponse-perceived benefitsof participation have declined 3. inadequate coverage

of the population-poor sampling frame 4. samplingerror-random sampling due to chance


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Field Experiment

Experimental study conducted in thefield, in real-world settings

Control over conditions is a bigproblem


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External Validation

Process of testing the validity of a measure,index,scale by examining its relation to other presumed

indicators of same variable

E.g. index of prejudice correlates with other indicatorsof prejudice


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Experimental Research

Searching for cause and effectThe classical experimental design helps usunderstand the logic of all research designs

Experiment is treated as a model againstwhich to evaluate other designs


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Experimental realism

Degree to which experiment

absorbs and involves its

participants


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Experimental group

Subjects who receive some

treatment


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Experimental design

Allows researcher to draw causalinferences and observe whether or not

the independent variable caused thedependent variable


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EPSEM-equal probability ofselection method

All members of the population have an equalchance of being selected in the sample

Is representative of the population from whichit is selected


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Elements

The individual members of the

sample


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Demonstrate Causality3 operations

1. covariation-two or more things varytogether(correlation) 2. nonspuriousness-a relation

between two variables that cannot be explained by athird variable 3. time order- demonstrate that the

assumed cause occurs first or changes prior to theassumed effect


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Demand Characteristics

Cues in an experiment that tells the participant whatbehavior is expected. In subtle ways the

experimenters words, tone of voice,gestures mayinadvertently demand desired results.To minimize

these the experimenter typically standardizesinstructions or write or tape record them.


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Criteria for CausalExplanations

1. Empirical association-variation in one variable isrelated to variation in another variable 2. appropriatetime order variation in dependent variable occurred

after the variation in the independent variable3.nonspuriousness when a relation between two

variables is not due to variation in a third variable


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Convenience sample

Researchers select a sample for studyon the basis of what is handy-e.g.

teachers using their classes


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Control group

Subjects who do not receive thetreatment


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Confidence level

The estimated probability that apopulation parameter lies within a

given confidence interval. 95 percentconfident or 99 percent conficent

C fid i l (3)


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Confidence interval (3)

Between 1Z and +1Z expect to find 68 percent of allsample means,between -1.96Z and +1.96Z find 95 % of all

sample means between -2.58Z and +2.58Z expect to find 99percent of all sample means

Confidence interval of -1.96to +1.96 about samplemean(.05),+2.58 and -2.58 is 99 out of 100,or 99 per cent

confidence interval (.01)


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Confidence interval (2)

If one knew the mean of all sample means(populationmean) and the standard deviation of these sample

means 9standard error of the mean) one couldcompute Z scores and determine the range within

which any percentage of the sample means can befound


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Confidence Interval

The range of values within whicha population parameter is

estimated to lie +-1.96 or +- 2.58


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Confidence Interval

If the distribution of sample means is normalor approximate normality, we can use the

properties of the normal curve to estimate thelocation of the population mean.


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Confederate

Person posing as a fellow participant in

an experiment who is an accomplice of

the experimenter


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Comparison group

group of subjects that is exposedto a different treatment from the

experimental group


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Weighting

Assigning different weights to cases that wereselected into a sample with different

probabilities of selection.,each case givenweight equal to the inverse of its probability of

selection

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Research Revision Topics