15-1

Chapter FifteenDATA PREPARATION AND

DESCRIPTION

15-2

Editing (Continued)

• What is it?– Detects errors and omissions, corrects

them when possible, and certifies that minimum data quality standards are achieved

• Purpose– To guarantee that data are accurate,

consistent with other information, uniformly entered, complete, and arranged to simplify coding and tabulation

15-3

Editing

• Field Editing– translation of ad hoc abbreviations

and symbols used during data collection

– validation of the field results. • Central Editing

– Thorough editing of entire data, including detection of fake interviews.

15-4

Coding

• Rules that guide the establishment of category sets– Appropriate to the research problem and purpose

(best partitioning of data)– Exhaustive (a large number of “other” responses

indicates non-exhaustiveness)– Mutually exclusive– Derived from one classification principle

15-5

Data Entry Options

• Optical scanning

• Voice recognition

• Keyboard

15-6

Data Entry Formats

• Database with full screen editor

• Spreadsheet

15-7

Descriptive Statistics

• Distribution Descriptors

– Location

– Spread

– Shape

15-8

Descriptive Statistics

• Location (Central Tendency)– Mean: arithmetic average

– Median: midpoint of the distribution

– Mode: the most frequently occurring value

15-9

Descriptive Statistics

• Spread (dispersion, variability)– Variance: the average of the squared deviations

from the distribution’s mean, – Standard Deviation: square root of variance– Range – Interquartile Range (midspread): the difference

between the first and third quartiles– Quartile deviation (semi-interquartile range): (Q1-

Q3)/2

15-10

Descriptive Statistics

• Shape– Skewness (sk): a measure of a

distribution’s deviation from symmetry • Positive (right) skewed vs. negative (left)

skewed– Kurtosis (ku): a measure of a

distribution’s peakedness (or flatness)• Postive (leptokurtic) vs. negative

(playyukurtic)