When constructing a Confidence Interval for the population mean and both the sam

Question

When constructing a Confidence Interval for the population mean and both the sample standard deviation and the population standard deviation are known, which of the following should be used?

A)normal distribution using the sample standard deviation

B)normal distribution using the population standard deviation

C)student-t distribution using the population standard deviation

D)student-t distributuion using the sample standard deviation

A study was done to determine the proportion of voters that feel that their local government is doing an adequate job. Of the 160 voters surveyed, 144 feel that their local government is doing an adequate job. Calculate the 95% confidence interval for the true proportion of voters that feel that their government is doing an adequate job.

A)(0.85, 0.95)

B)0.90

C)(0.80, 1.00)

D)(144, 160)

To reduce the error bound in a future study, which of the following should be done?

A)increase the sample size n

B)decrease the sample size n

C)conduct a biased survey

D)increase the confidence level

Explanation / Answer

Ans:

1) Option B is correct.

normal distribution using the population standard deviation.

2)sample proportion=144/160=0.9

z value for 95% CI is 1.96

95% CI for p

=0.9+/-1.96*sqrt(0.9*0.1/160)

=0.9+/-0.05

=(0.85,0.95)

Option A is correct.

3)when sample size,n is increased,margin of error reduced.

Option A is correct.

increase the sample size n

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