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.

Analysing Data from Independent Groups: Continuous and Ordinal Measures

Analysing data from independent groups: Continuous and ordinal measures

Key Terms

box and whisker plot

chi-square test

Cohen's d

confidence interval

continuous (interval) scale

control group

effect size

experimental design

homogeneity of variance

independent groups design

independent groups t-test

Mann–Whitney test

non-parametric test

normal distribution

pooled variance t-test


quasi-experimental design

standard deviations

standard error

type I error rate

unpooled variance t-test




This chapter tells you how to analyse data from experiments that use an independent groups (or between-subjects) design. It tells you how to get from charts and data to probability statements. You should be warned that when you turn the pages you will find equations with terrifying sequences of numbers and Greek symbols. They look much worse than they really are and you will not need ...

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