Understanding and Using Statistics in Psychology takes the fear out of psychological statistics to help students understand why statistics are carried out, how to choose the best test, how to carry out the tests, and then perform the analysis in SPSS. Emphasizing the place of statistical analysis in the process of conducting research, from design to report writing, this accessible and straightforward guide takes a non-technical approach, encouraging the reader to understand why a particular test is being used and what the results mean in the context of a psychological study. The focus is on meaning and understanding rather than numerical calculation.

### Relationships between Variables: Correlation and Regression

Relationships between variables: Correlation and regression

### What's in This Chapter?

• Association
• Correlation
• Regression
• Interpreting correlation and regression
• Calculating correlation coefficients: Pearson and Spearman
• Causality
• Using SPSS

### Key Terms

association

causal relationship

confidence interval

correlation coefficient

covariance

descriptive statistic

dicohotomania

equation for a straight line

eugenics

experiment

Fisher's z transformation

inferential statistic

Kendall's tau-a

line of best fit

non-parametric correlation

normal distribution

Pearson correlation coefficient

post hoc justification

power

proportion of variance

regression line

residual

sample statistics

scatterplot

Spearman correlation

standard deviation

standardised slope

statistical significance

y-intercept

### Introduction

So far in this book we have considered ways of comparing groups of individuals. In particular, we have looked at differences between groups. All our hypotheses so far have been along the lines of whether one set of scores is bigger, wider, more frequent etc. than another set of scores. Not all data are like that and sometimes we don't want to know about difference, we want to know about ...