Question 1 Which type of confidence interval should you use in this situation? A

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Question 1

Which type of confidence interval should you use in this situation? A sample of 25 different payroll departments found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. The distribution is approximately normally distributed. Find the 90% confidence interval for the average days worked of all payroll departments.

Question 2 (1 point)

Which type of confidence interval should you use in this situation? A sample of 400 racing cars showed that 80 cars cost over $700,000. Find the 99% confidence interval of the true proportion of racing cars costing over $700,000.

Question 3

Which type of confidence interval should you use in this situation? A sample of 6 adult elephants had an average weight of 12,200 pounds, with a sample standard deviation of 200 pounds. Find the 95% confidence interval of the true mean.

Question 4

Which type of confidence interval should you use in this situation? An economics professor randomly selected 100 millionaires in the United States. The average age of these millionaires was 54.8 years with a standard deviation of 7.9 years. What is the 95% confidence interval for the mean age of all United States millionaires?

Question 5

A lawyer researched the average number of years served by 45 different justices on the Supreme Court. The average number of years served was 13.8 years with a standard deviation of 7.3 years. What is the 95% confidence interval for the average number of years served by all Supreme Court justices?

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Question 6

A recent study of 750 zombies in Europe found that 35% of zombies were women. What is the 95% confidence interval of the true proportion of women in Europe who are zombies?

Question 7

Suppose you do a study of meditation to determine how effective it is in relieving pain. Sensory rates are measured for the sample of 20 subjects. The data yields a mean of 10.3 and a standard deviation of 2.0. Construct a 90% confidence interval for the mean sensory rate for the population from which you took the sample. Assume that population has a normal distribution of sensory rates.

1) a confidence interval for the mean using a table value from the standard normal distribution. 2) a confidence interval for the mean using a table value from the t distribution. 3) a confidence interval for a proportion using a table value from the standard normal distribution. 4) a confidence interval for proportion using a table value from the t distribution. 5) none of the above.

Explanation / Answer

Answering only 1 question as per Chegg policy.

1) Correct answer is B :

A t-table should be used instead of a normal distribution because number of observations is less than 30.

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