1. 15-1 Chapter Fifteen DATA PREPARATION AND DESCRIPTION

2. 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

3. 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.

4. 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

5. 15-5 Data Entry Options Optical scanning Voice recognition Keyboard

6. 15-6 Data Entry Formats Database with full screen editor Spreadsheet

7. 15-7 Descriptive Statistics Distribution Descriptors –Location –Spread –Shape

8. 15-8 Descriptive Statistics Location (Central Tendency) –Mean: arithmetic average –Median: midpoint of the distribution –Mode: the most frequently occurring value

9. 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

10. 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)