3.3 - One Quantitative and One Categorical Variable

Often times we want to compare groups in terms of a quantitative variable.  For example, we may want to compare the heights of males and females. In this case height is a quantitate variable while biological sex is a categorical variable. Graphs with groups can be used to compare the distributions of heights in these two groups. Below you will find examples of constructing side-by-side boxplots, dotplots with groups, and histograms with groups using Minitab Express. The side-by-side boxplots allow us to easily compare the median, IQR, and range of the two groups. The dotplots with groups and histograms with groups allow us to compare the shape, central tendency, and variability of the two groups.

MinitabExpress  – Side-by-Side Boxplots

To create a side-by-side boxplots in Minitab Express:

  1. Open the data set:
  2. On a PC or Mac: GRAPHS > Boxplot
  3. Select With Groups
  4. Double click the variable Height in the box on the left to insert the variable into the Y variable box
  5. Double click the variable Biological Sex in the box on the left to insert the variable into the Group variable box
  6. Click OK

This should result in the following side-by-side boxplots:

Boxplot of Height

Video Walkthrough

Select your operating system below to see a step-by-step guide for this example.

MinitabExpress  – Dotplots with Groups

To create dotplots with groups in Minitab Express:

  1. Open the data set:
  2. On a PC or Mac: GRAPHS > Dotplot
  3. Select With Groups
  4. Double click the variable Height in the box on the left to insert the variable into the Y variable box
  5. Double click the variable Biological Sex in the box on the left to insert the variable into the Group variable box
  6. Click OK

This should result in the following dotplots with groups:

Dotplot of Height

Video Walkthrough

Select your operating system below to see a step-by-step guide for this example.

MinitabExpress  – Histograms with Groups

To create histograms with groups in Minitab Express:

  1. Open the data set:
  2. On a PC or Mac: GRAPHS > Histogram
  3. Select With Groups
  4. Double click the variable Height in the box on the left to insert the variable into the Y variable box
  5. Double click the variable Biological Sex in the box on the left to insert the variable into the Group variable box
  6. Click OK

This should result in the following histograms with groups:

Histogram of Height

Video Walkthrough

Select your operating system below to see a step-by-step guide for this example.