Testimate Guide

This guide will show you how to use the testimate plugin to perform traditional statistical tests and estimates.

It will also show you how to collect information from multiple tests, and use that to learn more about how these tests and estimates work.

The basics

The dataset (from NHANES) is a sample of 573 USA-ians, aged 16, 17, and 18. We want to know which gender’s pulse is faster, and if that difference might just be due to chance. Here is what typical testimate output looks like:

Here is the basic pattern for using testimate to perform tests and make estimates:

  1. Have your data in a CODAP window.
  2. Choose testimate from the Plugins menu.
  3. Drag an attribute you’re studying (e.g., pulse) into the box on the left. If you have more than one attribte involved, put the “outcome” attribute here if there is one.
  4. If there is another attribute, perhaps a “predictor” attribute (gender), drag it into the box on the right.
  5. Choose which test you want from the menu (difference of means).
  6. Adjust any test parameters that need adjusting.

Try reproducing the test of pulse grouped by gender in the live example below. We’ve already done Step 1.

Of course, before you do a test, you make a graph, right?

Now, by all means, play with the data by dragging different attributes into the spots in testimate. See what tests are available!

Tip

Everything should be pretty self-explanatory … except logistic regression. That has a separate chapter, as you can see at left.

What if a numerical attribute is supposed to be categorical?

In your playing around, suppose you wanted to see if there was any significant association between age and gender. Like, in our dataset of 16, 17, and 18-year-olds, was the gender balance different in one of those years?

For that, we should run a chi-squared test for independence, using those two attributes.

The problem is, when we try to set it up, the test for independence does not appear in the menu. What gives?

The problem is that that test requires two categorical attributes, and age is numeric. Fortunately, there’s an easy solution.

In your age box in testimate, you can see a gray button labeled 123. That’s the signal that testimate thinks it’s numeric. Click it! It will change to abc (i.e., categorical), and you will find the test you want in the menu.