The average verbal score for the girls is 24, compared with an average
score of 18 for the boys.
Because these three strategies produce similar data, they also tend to use
similar statistical techniques. For example, t tests and analysis of variance are
used to evaluate mean differences and chi-square tests are used to compare
proportions.
Correlational studies do not involve comparing different groups of scores.
Instead, a correlational study measures two different variables (two different
scores) for each individual in a single group and then looks for patterns within the set of scores (see Figure 6.2). If a correlational study produces numerical
scores, the data are usually evaluated by computing a correlation (such as the
Pearson correlation). If the data consist of nonnumerical classifications, the
statistical evaluation is usually a chi-square test.
Descriptive studies are intended to summarize single variables for a specific
group of individuals. For numerical data, the statistical summary usually consists
of a mean, or average, score. If the data are nonnumerical classifications, the summary
is typically a report of the proportion (or percentage) associated with each
category. For example, the average student sleeps 7 hours a day and eats two pizzas
a week. Or, 58% of the students report having failed at least one course.