Effect Size &
Hypothesis Testing

The Z test reflects the location of the sample mean within the distribution of sample means (as specified by the null hypothesis).  The larger the Z test, the worse job the null hypothesis did in predicting the observed sample mean.  The larger the Z-test, the smaller the "Sig. (2-tailed)", indicating that for a true null hypothesis, an extreme observed sample mean can occur but is rare.   For a two-tailed hypothesis test, and alpha at .05, we would reject the null hypothesis when the "Sig. (2-tailed)" is .05 or less.  

Note that for a large sample size, even a seemingly small difference between the observed sample mean and the predicted sample mean value can be considered a rare and unlikely event.  Thus, with very large sample sizes, we may be able to reject the null hypothesis for even a small trivial difference between the null specified population mean and the observed sample mean.

Cohen's d is a measure of effect size.  A large effect size would be considered very meaningful, whereas a very small effect size would typically be considered of little or no value.  Cohen's d indicates the difference (as measured in standard deviations) between the observed sample mean and the specified population mean.

Resources/Options

• View the video tutorial for this game.

• Open the game in Full Screen mode

To earn credit for this activity:

1. Click the 'Accommodations' button on the game menu.

2. Using the number pad (in the Accommodation dialog box), type the passcode provided by your instructor.

3. Click the 'Continue' button.  Doing so will return you back to the game menu.

4. Then click 'Start' to begin the game. 

5. When you complete the task with a score of 85% or greater, you will be given a completion code.  To view this completion code, click on the 'Completion Code' button.

6. To get credit for having completed the activity,  provide the completion code as your answer (e.g., to a quiz question).  If the completion code is not yet available (e.g., performance was less than 85%), then click the 'Continue' button to re-do the activity. 

Accommodations include: 

• Screen Reader (click the 'Screen Reader' button)

• Unlimited decision time (e.g., Click the 'Accommodations' button, then type #17 by itself or at the end of a passcode.  Click 'Continue').

Please notify your instructor if requesting these accommodations.

Instructors can modify games and set up quizzes rather easily.  Check out game modifications.