DATA DESCRIPTION Research Methods College of Public and Community Services University of Massachusetts at Boston ©2012 William Holmes 1

USES OF DATA DESCRIPTION Checking data Describing individual variables Examining relationships between variables Enhancing understanding 2

CHECKING DATA Review and correct sources of data, paper forms. Enter data in computer with error checking. Examine frequency distributions for invalid codes. Check variable labels and value labels for accuracy. Save a backup copy of the data. 3

DATA SOURCE REVIEW AND CORRECTION Look for ambiguous responses and clarify. Look for missing data and obtain if possible. Look for marginal notes and take necessary action. 4

ENTERING DATA WITH ERROR CHECKING Choose familiar data entry program : database, spreadsheet, statistical. Provide training for data entry. Have codebook available. Use valid range checks if available. Use “validation” (double entry) if available. 5

EXAMINE FREQUENCY DISTRIBUTIONS: 1 Generate Frequency Distributions TOTALVALID VARIABLECODENPCT PCT SexMale Female Missing 1 2 QualifiedYes No

EXAMINE FREQUENCY DISTRIBUTIONS: 2 Check for valid codes Check for missing data Check variable labels Check variable names 7

EXAMINE FREQUENCY DISTRIBUTIONS: 3 Check distribution for symmetry Check distribution for multiple modes Check central tendency Check dispersion Check you have a backup of data 8

ODDITIES OF DISTRIBUTIONS Number of peaks: modes Skewness: imbalance Flatness: kurtosis 9