This test is used to test a claim about the standard deviation of a single population, such as this claim: "The IQ scores of statistics students have a standard deviation equal to 15."
Caution: Be careful to avoid confusion between the POPULATION standard deviation given in the original claim, and the sample standard deviation found from the sample data. For example, if testing the claim that IQ scores of statistics students have a standard deviation equal to 15, and sample data consist of n = 36 and s = 12, the "Claimed StDev" is 15 and the "Sample StDev" is 12.
First select the format of the original claim that is to be tested. Note that there are 6 different choices, which can be viewed by clicking on the small box to the right of the default claim ("Pop. StDev = Claimed StDev"). Use the up/down arrow keys to highlight the desired choice, then click on that desired choice. STATDISK will determine the appropriate null hypothesis from the claim selected.
Significance (level): Enter a positive value in decimal form, such as 0.05.
Claimed StDev: Enter the value of the standard deviation used in the original claim.
Enter the sample size n as a positive whole number.
Enter the value of the sample mean.
Enter the value of the SAMPLE standard deviation s.
Click on the Evaluate button to obtain the results.
Click on the Print button to print the results.
Click on the Plot button to display a graph showing the distribution with the test statistic and critical value(s).
To close the window, click on the X at the top of the module window.