Confidence Interval for a Population Mean

In a crash test of 15 troopers, collision repair costs are found to have a distribution that is approximately normal, with a mean of $1800 and a standard deviation of $950. Construct a 99% confidence interval for the repair cost. 

• (1070, 2530)

• (1273, 2326)

• (1799, 1801)

• None of these.

A sample of 30 women finds the mean height to be 62.3 in and the standard deviation to be 1.5 in. Find the margin of error of women's heights with a 95% CL.

• 699

• 0.56

• 0.537

• 19.325

A 90% confidence interval for the mean speed driven by cars on East Main St. is given by (21, 45). What was the sample mean of this study?

• 12

• 24

• 33

• None of these.

A 90% confidence interval for the mean speed driven by cars on East Main St. is given by (21, 45). What was the margin of error of this study?

• 12

• 24

• 33

• None of these.

Find the t* value for a 99% confidence interval with a sample of 23 people.

• 1.714

• 1.711

• 2.064

• None of these.

The 90% interval for a statistics test was given by 72 +- 7. What is the lower bound for the interval?

• 7

• 72

• 65

• 79

In a random sample of 10 adults, the mean waste generated per person per day was 4.50 pounds and the standard deviation was 1.21 pounds. Assume that the random variable is normally distributed. Construct a 99% confidence interval for the population mean. Use the following rounding off rules: * critical t-value - 3 d. p. * margin of error - 1 d. p.

In a random sample of 11 college football players, the mean weekly time spent weightlifting was 7.2 hours. Assume that the population data is normally distributed. From past studies, the population standard deviation was 1.9 hours. What is the margin of error for a 90% confidence interval? (1 d. p.)

In a random sample of 11 college football players, the mean weekly time spent weightlifting was 7.2 hours. Assume that the population data is normally distributed. From past studies, the population standard deviation was 1.9 hours. Interpret the results of the 90% confidence interval for the population mean weekly time spent weightlifting.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.3 hours and 8.1 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.2 hours and 8.0 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.4 hours and 8.2 hours.

• With 90% confidence, we can say that the population mean weekly time spent weightlifting is between 6.2 hours and 8.3 hours.

What is the critical t-value for a 95% confidence level when the sample size is 24? (3 d. p.)