Question

In: Statistics and Probability

A simple random sample of 60 items resulted in a sample mean of 90. The population...

A simple random sample of 60 items resulted in a sample mean of 90. The population standard deviation is σ = 10. (a) Compute the 95% confidence interval for the population mean. (Round your answers to two decimal places.) (b) Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean. (Round your answers to two decimal places.)

Solutions

Expert Solution

Solution :

Given that,

Z/2 = 1.96

(a)

n = 60

Margin of error = E = Z/2* ( /n)

= 1.96 * (10 / 60)

= 2.53

At 95% confidence interval estimate of the population mean is,

- E < < + E

90 - 2.53 < < 90 + 2.53

87.47 < < 92.53

(87.47 , 92.53)

(b)

n = 120

Margin of error = E = Z/2* ( /n)

= 1.96 * (10 / 120)

= 1.79

At 95% confidence interval estimate of the population mean is,

- E < < + E

90 - 1.79 < < 90 + 1.79

88.21 < < 91.79

(88.21 , 91.79)


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