10 Describing Data

Descriptive statistics are used to summarize, organize, and overall describe our sample data.

We explore our data partly to describe our data and partly to check our data before performing inferential statistics. jamovi puts all our descriptive statistics into one useful analysis under the Exploration button (within the Analyses tab) called Descriptives. Whenever you want to understand the measure of central tendency or dispersion of a single variable (e.g., what is the mean score on a particular scale?) then you’ll go to the Descriptives analysis under Exploration.

In the Descriptives analysis, these are under the Statistics drop-down menu. There are a ton of possible options!

1. Sample size: you can ask for the sample size (N) and number of missing values (Missing).
2. Percentile values: these are useful for creating quartiles (Cut points for 4 equal groups) or Percentiles of various sizes.
3. Dispersion: you should already be familiar with most of the measures of dispersion, particularly the Minimum and Maximum and the Std. deviation (SD) and Variance (which is just SD²). We’ll learn about the S. E. Mean later.
4. Central Tendency: similarly, you should also be familiar with all of the measures of central tendency: Mean, Median, Mode, and Sum.
5. Distribution: you should also be familiar with both Skewness and Kurtosis and later we will learn what those values mean and how that helps us test for normality.
6. Normality: lastly, there is a statistical test for normality called the Shapiro-Wilk test that we will learn about later.

You might be wondering how we report descriptive statistics in a Results section. Sometimes we use tables and figures to do this, or sometimes means and standard deviations are written in the text. We shall look at examples of figures in the next section, and you will see examples of tables and in-text descriptive statistics later in the book.