15-1 Chapter Fifteen DATA 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)