Establish Whether populations have equal variance

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Discussion Overview

The discussion revolves around determining whether two populations have equal variance based on provided data from two days of measurements. Participants are seeking guidance on how to apply the F-test for this purpose, including the necessary calculations and interpretations.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Participants provide data for two days, including means, standard deviations, and sample sizes.
  • Some participants suggest using the F-test to compare the variances of the two populations.
  • There is a request for clarification on how to execute the F-test, including the calculation of the F-test statistic.
  • Participants express uncertainty about the meaning of the F-test and the steps required to implement it.
  • One participant mentions looking up critical values in an F-table based on significance level and degrees of freedom.

Areas of Agreement / Disagreement

Participants generally agree that the F-test is the appropriate method for comparing variances, but there is no consensus on the specific steps or interpretations involved in executing the test.

Contextual Notes

Participants have not provided detailed assumptions or definitions related to the data or the F-test, and there are unresolved questions about the implementation of the test.

Who May Find This Useful

Individuals interested in statistical methods for comparing variances, particularly those seeking assistance with the F-test and its application in practical scenarios.

Wrightomatic
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day 1
distance equals 52.175m, std = 0.015m and n = 10

day 2
distance equals 52.193m, std = 0.021m and n = 11

Establish whether the two populations have equal variance at the 0.05 signifcance level. Can someone help me out with how to get to the answer and what the answer actually is?
 
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Wrightomatic said:
day 1
distance equals 52.175m, std = 0.015m and n = 10

day 2
distance equals 52.193m, std = 0.021m and n = 11

Establish whether the two populations have equal variance at the 0.05 signifcance level. Can someone help me out with how to get to the answer and what the answer actually is?

Welcome to MHB, Wrightomatic! :)

The F-test is the appropriate test to compare variances.
Do you know how to execute it?
 
No sorry i don't know how that is why I am asking. Could you please demonstrate how to apply such a test for the given data?

Thanks for your help :)
 
Wrightomatic said:
No sorry i don't know how that is why I am asking. Could you please demonstrate how to apply such a test for the given data?

Thanks for your help :)

The F-test statistic is $F=\dfrac{s_1^2}{s_2^2}$, where $s_1^2$ is the larger of the 2 variances.
Can you calculate that?
 
Yes I can calculate that but what does the F test mean? Like ill get the value for F then do i need to do anything else. As you can probably tell I have absolutely no idea how to do the test or how to implement it.

Could you possibly give me all the steps/formulas i will need and then I can work through it and check the final answer with you?
 
Wrightomatic said:
Yes I can calculate that but what does the F test mean? Like ill get the value for F then do i need to do anything else. As you can probably tell I have absolutely no idea how to do the test or how to implement it.

Could you possibly give me all the steps/formulas i will need and then I can work through it and check the final answer with you?

Well, you can find the steps/formulas for instance here.

The F-test tests if 2 variances are different.
You should look up the critical value in an F-table for the appropriate significance and degrees of freedom (see the article).
If your calculated F-value is greater than this critical value, your variances are different.
If it is lower, the variances are assumed equal.
 

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