STEP-BY-STEP TECHNOLOGY GUIDE: F Test for Comparing Two Population Standard Deviations

TI-83/84

F Test

  • Step 1 If you have the raw data, enter the two samples into L1 and L2.
  • Step 2 Press Stat, highlight TESTS, and select 2-SampFTest. Press ENTER.
  • Step 3
    1. If you have the raw data, highlight Data and press ENTER. For List1, enter L1; for List2, enter L2; for Freq1 and Freq2, put 1. Highlight the correct form of the alternative hypothesis and press ENTER. Highlight Calculate and press ENTER.
    2. If you have the summarized data, highlight Stats and press ENTER. For Sx1, enter the sample standard deviation of the first sample, and for n1, enter the size of the first sample. For Sx2, enter the sample standard deviation of the second sample, and for n2, enter the size of the second sample. Highlight the correct form of the alternative hypothesis and press ENTER. Highlight Calculate and press ENTER.

p-value of an F test

  • Step 1 Press 2nd VARS to bring up the list of distributions.
  • Step 2 Press the down arrow key until you reach Fcdf(. Press ENTER.
  • Step 3 Enter the left endpoint, comma, the right endpoint, comma, df1, comma, df2, close parenthesis. Then press ENTER.

EXCEL

  • Step 1 Enter the samples from populations 1 and 2 into columns A and B.
  • Step 2 Select the Data menu, click Data Analysis, and select F Test Two-Sample for Variances.
  • Step 3 Put the cursor in the Variable 1 Range and highlight the data in column A. Put the cursor in the Variable 2 Range and highlight the data in column B. Enter the value for alpha (α). Then click OK.

MINITAB

  • Step 1 If you have the raw data, enter the samples from populations 1 and 2 into columns C1 and C2.
  • Step 2 Select the Stat menu, highlight Basic Statistics, and select 2 Variances….
  • Step 3
    1. If you have the raw data, select Each sample is in its own column, and enter C1 for Sample 1 and C2 for Sample 2.
    2. If you have the summarized data with sample standard deviations, select Sample standard deviations, and enter the sample sizes and sample standard deviations in the appropriate cells.
    3. If you have the summarized data with sample variances, select Sample variances, and enter the sample sizes and sample variances in the appropriate cells.
  • Step 4 Click Options… and select a Confidence level, which should equal 1 – α. Enter the Hypothesized ratio, select the form of the Alternative hypothesis, and then click OK twice. There is both graphical output as well as output to the session screen.

CRUNCHIT!

p-value of an F test

  • Step 1 Click Distribution Calculator > F.
  • Step 2 Enter df1 and df2. Under the Probability tab, choose < or > from the drop-down menu, and input Fdata. Click Calculate.