Compute a correlation:
Pearson Correlation Coefficient
To compute a Pearson correlation coefficient using SPSS, suppose we test the hypothesis that greater mobile phone use is associated with increased stress, as has been tested in published research studies (see Murdock, Gorman, & Robbins, 2015; Reid et al., 2009; Thomée, Härenstam, & Hagberg, 2011). To measure mobile phone use, we can use the 27-item Mobile Phone Problem Use Scale (MPPUS; Bianchi & Phillips, 2005). To measure stress, we can use the 10-item Perceived Stress Scale (PSS; Cohen & Williamson, 1988). Using these measures, we will enter the data shown in Figure 8.11 to compute a Pearson correlation coefficient using SPSS.
Click on the Variable View tab and enter MPPUS in the Name column; enter PSS in the Name column below it. Reduce the value to 0 in the Decimals column for both rows.Click on the Data View tab. Enter the data for MPPUS in the first column; enter the data for PSS in the second column.Go to the menu bar and click Analyze, then Correlate, and then Bivariate to display a dialog box.Using the arrows, move both variables into the Variables box.Select OK, or select Paste and click the Run command.
The SPSS output table, shown in Table 8.3, is set up in a matrix with MPPUS and PSS listed in the rows and columns. Each cell in the matrix gives the direction and strength of the correlation (r = .540 for mobile phone use and stress; this value is shown with an asterisk for significant correlations), the significance (p = .014; how to interpret a p value is described in Chapters 10–12 and 14), and the sample size (N = 20). To make a decision: If a correlation is significant, then the decision is that the correlation observed in the sample will also be observed in the larger population from which the sample was selected. We can report a correlation in a research journal using the guidelines provided in the Publication Manual of the American Psychological Association (APA, 2009). Using these guidelines, we state the value of r, the p value, and the sample size as shown:
A Pearson correlation indicates that greater mobile phone use is associated with greater perceived stress, r =.540, p =.014, N = 20.”
