5.6 Putting It All Together

This chapter focused on describing data in jamovi. The big idea is simple but important: the descriptive statistics you choose should match the kind of variable you are describing.

Chapter Recap

You should now be able to:

  • check variable setup before running descriptives
  • use frequencies and percentages for categorical variables
  • use means, standard deviations, ranges, skewness, and kurtosis for continuous variables
  • describe continuous variables across groups using Split by
  • decide whether a paragraph or table is clearer
  • avoid overclaiming from descriptive statistics

Quick Guide: Which Descriptive Statistics Should I Use?

Variable type Useful descriptive statistics Usually avoid
Nominal Frequencies, percentages, mode Mean, standard deviation
Ordinal Frequencies, percentages, median, range or IQR Treating categories as if distances are definitely equal
Continuous, roughly symmetric Mean, standard deviation, minimum, maximum Reporting only the range
Continuous, skewed or with outliers Median, IQR, minimum, maximum; sometimes mean and SD with caution Relying only on the mean
Continuous variable split by groups Group-specific mean, SD, median, sample size, and missing values Claiming group differences are “real” before inferential testing

The goal is not to report every statistic jamovi can produce. The goal is to choose the statistics that help someone understand the variable.

Common Mistakes

Watch for these common mistakes:

  • reporting a mean for a nominal variable
  • forgetting to check variable setup before running descriptives
  • ignoring missing values
  • reporting every statistic jamovi provides
  • treating descriptive differences as statistical significance
  • failing to describe groups separately when the research question is group-based
  • not checking whether values fall in the expected range

Applied Practice

Imagine a dataset includes the following variables:

Variable Description
Condition Participants were assigned to control or treatment
Age Participant age in years
Class_Level First-year, sophomore, junior, or senior
Stress_Mean Average score on a 1 to 5 stress scale

Answer these questions:

  1. Which variables are categorical?
  2. Which variables are continuous?
  3. Which variables should be described with frequencies and percentages?
  4. Which variables should be described with means and standard deviations?
  5. If you wanted to describe stress separately by condition, which variable would go in Split by?
Answers
  1. Condition and Class_Level are categorical.
  2. Age and Stress_Mean are continuous.
  3. Condition and Class_Level should be described with frequencies and percentages.
  4. Age and Stress_Mean should usually be described with means and standard deviations, though you should also check the distribution.
  5. Stress_Mean would go in the Variables box and Condition would go in the Split by box.

Looking Ahead

Descriptive statistics give us useful summaries, but they can also hide important patterns. Two variables can have the same mean and standard deviation but very different shapes, outliers, or group patterns. That is why the next chapter focuses on visualizing data.