Historically, the average time it takes Jessica to swim the 200 meter butterfly

Question

Historically, the average time it takes Jessica to swim the 200 meter butterfly is 148.4 seconds. Jessica would like to know if her average time has changed. She records her time on 50 randomly selected occasions and computes the mean to be 147.8 seconds with a standard deviation of 2.3 seconds. use alpha = .05 The hypothesis to be tested is: H0: mu=148.4 vs. Ha: mu not equal 148.4 The test statistic is: z=-1.845 Please state the correct conclusion. A. Fail to reject the null hypothesis. B. Reject the null hypothesis. C. Not enough information is given. D. Accept the null hypothesis.

Explanation / Answer

P-value = 2 * P(Z < -1.845)

            = 2 * 0.033

           = 0.066

Since the P-value is grater than the significance level (0.066 > 0.05), so we should not reject H0.

Option - A) Fail to reject the null hypothesis.

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