Did I Get This – Type I and Type II Errors

Published: March 18th, 2013

Category: Activity 2: Did I Get This?

In the following activities, you are asked to describe each type of error in context (in the words of the problem or scenario).


Consider the following hypotheses, which we have seen before.

  • Ho: The average time full-time undergraduate college students study outside of class per week is 30 hours.
  • Ha: The average time full-time undergraduate college students study outside of class per week is not 30 hours.


In a previous example, we had the following hypotheses:

  • Ho: The mean concentration in the shipment is the required 245 ppm.
  • Ha: The mean concentration in the shipment is not the required 245 ppm.

From the results obtained, we rejected the null hypothesis and concluded with very little doubt that the mean concentration in the shipment is not the required 245 ppm.


In another example, we had the following hypotheses.

  • Ho: Performance on the SAT is not related to gender (males and females score the same).
  • Ha: Performance on the SAT is related to gender – males score higher.

The data did not provide enough evidence for rejecting Ho. So there was not enough evidence that males score higher than females. The difference observed was not statistically significant.


This document is linked from Errors and Power.