Psychologists collect various kinds of data. The data could be numerical scores, people’s ranking of some item, or categories such as gender or race. Each type of data goes by a different name.

Numerical scores are called: measurement or scale data.
Rankings are called: ordinal data
Categories such as gender are called: nominal data.

You want to be able to summarize each type of data. How to do it? You will learn that to summarize data, you will need to determine:

Measures of central tendency: They tell you about the most typical scores.
Measures of variability: They tell you about how the scores are spread out.