1. If you increase the sample size, the width of confidence interval will A. be

Question

1. If you increase the sample size, the width of confidence interval will

A. be the same.

B. also increase.

C. decrease

D. depends on the population size

2. A political party wishes to estimate the proportion of voters that support the party in a particular state. The party will poll a random sample of n voters from the state. Which of the following is likely to result in the largest margin of error?

A. n = 500, confidence level = 95%

B. n = 500, confidence level = 99%

C. n = 500, confidence level = 90%

D. n = 100, confidence level = 95%

E. n = 100, confidence level = 90%

3. Suppose we have a population that its distribution is normal. What minimum sample size we should select in order to have an approximately normal distribution (symmetric) for the corresponding sample mean?

A. About 10% of the population size

B. It is based on population standard deviation

C. Any size

D. 30

4. Do employees of car manufacturing perform better at work with music playing? The music was turned on during the working hours of a car manufacturing with 125 employees, and their productivity level averaged 8.5 with a standard deviation of 2. Assuming productivity level of 7.7 for the car manufacturing employees in general, what can we conclude at 90% level of confidence?

A. Employees perform better at work with music playing.

B. Employees performance doesn’t do anything with music playing.

C. Not enough information to estimate employees’ performance with music playing

D. None of the above.

Explanation / Answer

1. If you increase the sample size, the width of confidence interval will decrease

2. D. n = 100, confidence level = 95% is likely to result in the largest margin of error.

3. C. Any size

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