Psyc.301SPSS Lab Session

Spring 2014

Data screening & Transformation

Recode– To recode negatively worded items– To collapse continuous variables into categorical ones

• Recode into same variable• Recode into different variable

• Recoding negatively worded scale items– Transform ─ Recode into SAME variables (to overwrite original data)– Select variables and move it to Variables box ( k1, k6, k7, k8, k10, k13, k15, and

k16 in week3 dataset.sav data)– Click on Old and New Values– Type old value in old value box new value in new value box and click Add – Repeat the last step for the remaining values to be changed– Click on Continue and Ok

• To collapse a continuous variable – Transform ─ Recode into different variables (to retain original data)– Select variable and move it to Numeric Variable-Output Variable box– Type a new name in name box and a new label in label box, and click on

change– Click on Old and New Values– Click on second Range and type the median in the box– Type new value in new value box and click Add – Click on third Range, type the median plus 1 in the box– Type new value in new value box and click Add – Click on Continue and Ok

Compute

• Usually to obtain composite scores of itemsExample: kssc scale items.sav

• Compute if … («compute if certain condition is met»)

• COMPUTE (example of calculating a total score)

– Transform ─ Compute variable– Type a name in Target Variable box– Select variables and move to Numeric expression box, click on +– Select other variables and repeat the same step by clicking on + – click on Ok

• New composite variable is added to the data

• COMPUTE IF…

– Transform ─ Compute variable– Type a name in Target Variable box– Select variables and move to Numeric expression box, click on +– Select other variables and repeat the same step by clicking on +– Click on If, select Include if case satisfies condition,– Select the relevant variable and move it to the box, select the required operator button– click on Continue and Ok

Descriptive statistics

• Mean• Mode• Median• Standard deviation• Normality measures: skewness kurtosis• Normal distribution• Negatively skewed distribution• Positively skewed distribution• Histogram

Data distribution

Select cases• If you want to analyze only a part of the dataset which mets a certain condition

• Selection of specified cases using the If option• Selection of a random sample of cases using the Sample option• Selection of cases based on time or case range using the Range option

• Example: Select the first 5 cases for the analysis:

– Data ─ Select cases ─ If condition is satisfied ─ If– Select the relevant variable and move it to the box– Click on the relevant operator to add it into the box– Type if any other values are required (example: id<=5)– Click on Continue and Ok

• The cases after 5 are crossed in the data, analysis can be conducted by using only the first 5 cases

• Example 2: Selecting female cases• Example 3: Selecting those having depression scores above 16.