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.

Samples, Populations and the Normal Distribution

Samples, populations and the normal distribution

What's in This Chapter?

• Samples and populations
• The normal distribution (continued)
• z-scores
• The standard error
• Using SPSS

Key Terms

central limit theorem

descriptive statistics

generalisations

histogram

inferential statistics

infinity

normal distribution

parameters

population

probability

random sample

representative

sample

sampling distribution of the mean

standard error

uncertainty

variation

volunteer sample

z-score

Introduction

This chapter is about the tricky task of selecting a sample and making sense of the data you get from it. We often take for granted that the results from one group of people will be similar to those of another group, but why should we? If we carried out our opinion poll in the middle of a shopping centre we might get very different results from those we would get in the Tap Room of the Dog and Partridge. And then there is the matter of the normal ...