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Unit 32: Hypothesis Concerning Standard Deviation

7. In one sample of 10 observations from a normal population, the sum of squares of the Notes
deviations of sample values from their mean is 100.4 and in another sample of 12
observations from another normal population, the sum of squares of the deviations of
sample values from their mean is 115.5. Test at 5% level whether the two normal populations
have the same variance?

Hint : Use F - test.
8. In a test given to two groups of students, the marks obtained were as follows:
Group A : 18, 20, 36, 50, 49, 36, 34, 49, 41.

Group B : 29, 28, 26, 35, 30, 44, 46.
Assuming that the marks obtained follows normal distribution, examine at 5% level of
significance whether the two groups of students can be regarded to have come from
populations with same standard deviation?
Hint : Use F - test.

Answers: Self Assessment

1. size 2. F - distribution 3. variance ratio 4. confidence limits

32.9 Further Readings

Books Sheldon M. Ross, Introduction to Probability Models, Ninth Edition, Elsevier
Inc., 2007.
Jan Pukite, Paul Pukite, Modeling for Reliability Analysis, IEEE Press on
Engineering of Complex Computing Systems, 1998.

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