When research psychologists run a study, they collect a set of measurements as numbers.
In cognitive psychology experiments for example
a common measurement is the participant's’ reaction time, measured in milliseconds.
Each participant’s reaction time is referred to as their raw score or datum, which is the singular of the word data.
All the raw scores from the study together make up a data set.
To understand these data and identify patterns
researchers often arrange the data in a histogram plot from lowest to highest values.
The histogram allows them to see at a glance how the scores are grouped
which helps them determine the results of the study.
However, when data sets contain hundreds or even thousands of raw scores
psychologists calculate numbers, called descriptive statistics
that allow them to summarize important characteristics of the distribution.
These statistics allow us to describe the data in terms of the center of the data and the spread of the data.
Picking the right descriptive statistic is key to interpreting data correctly.
That is what we will examine in this activity.