Hypothesis Test for Two Variances:

- When to use it: To test if the variances of two populations are equal

For more information about Hypothesis Test for Two Variances click here.

## F-Test Example in Excel

Let's compare certain engine head dimensions from two different production lines. A sample of 10 items was taken from line 1 and a sample of 12 items was taken from line 2.

Line 1 | Line 2 |
---|---|

415.20 | 415.23 |

415.20 | 415.24 |

415.23 | 415.18 |

415.16 | 415.24 |

415.22 | 415.24 |

415.15 | 415.16 |

415.23 | 415.15 |

415.18 | 415.22 |

415.19 | 415.22 |

415.20 | 415.16 |

415.19 | |

415.23 |

We will use Excel to perform a hypothesis test of equal variances of the two lines using α = 0.05 and assuming the samples come from normal distributions.

## Using Excel

Select Data, Data Analysis, F-test Two-sample for Variances. Enter the appropriate range inputs, and then click OK.

Excel should calculate the following:

Since 0.233 = p-value > \( \alpha \) = 0.05 the equality of the two variances is not rejected.

## Running a two sample F test:

## Do it yourself

Step 1: Go to "Attachments" on the bottom of this page and dowload the Excel spreadsheet.

Step 2: Follow the steps teached in the video above and solve the exercises in the Excel spredsheet dowloaded.

Step 3: Answer the questions in the Interactive Content below.

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