# Two machines are used to package laundry detergent. It is known that weights of boxes are normally

## Question:

Two machines are used to package laundry detergent. It is known that weights of boxes are normally distributed. Four boxes from each machine have their contents carefully weighed, with the following results (in grams):

An engineer wishes to test the null hypothesis that the mean weights of boxes from the two machines are equal. He decides to assume that the population variances are equal, reasoning as follows:

The sample variances are s21 = 7.00 for machine 1 and s22 = 17.33 for machine 2. The F statistic for testing for equality of population variances is F3,3 = s22/s21= 2.48. The upper 10% point of the F3,3distribution is 5.39. Since the null hypothesis specifies that the variances are equal, I determine that the P-value is greater than 2(0.10) = 0.20. Therefore I do not reject the null hypothesis, and I conclude that the variances are equal.

a. Has the F test been done correctly?

b. Is the conclusion justified? Explain.

Distribution
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