(Round all intermediate calculations to at least 4 decimal places.) A random sam

Question

(Round all intermediate calculations to at least 4 decimal places.)

A random sample of 28 observations is used to estimate the population variance. The sample mean and sample standard deviation are calculated as 67.5 and 6.1, respectively. Assume that the population is normally distributed. Use Table 3.

Construct the 90% interval estimate for the population variance. (Round your answers to 2 decimal places.)

Construct the 99% interval estimate for the population variance. (Round your answers to 2 decimal places.)

(Round all intermediate calculations to at least 4 decimal places.)

A random sample of 28 observations is used to estimate the population variance. The sample mean and sample standard deviation are calculated as 67.5 and 6.1, respectively. Assume that the population is normally distributed. Use Table 3.

Explanation / Answer

a)

margin of error = 1.645 * 6.1/sqrt(28) = 1.8963

upper bound = 67.5 + 1.8963

lower bound = 67.5 - 1.8963

hence confidence interval is 65.60 to 69.40

b)

margin of error = 2.576 * 6.1/sqrt(28) = 2.97

upper bound = 67.5 + 2.97

lower bound = 67.5 - 2.97

hence confidence interval is 64.53 to 70.47

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