AP Stats Confidence Intervals for a Mean

A study of a large local high school tried to determine the mean amount of money that each student had saved. The study surveyed a random sample of 97 AP students in the high school and found a mean savings of 4100 dollars with a standard deviation of 500 dollars. Which conditions are met for calculating a confidence interval? Check all that are met.

• Random Condition

• 10% Condition

• Normal/Large Counts Condition

A study of a large local high school tried to determine the mean amount of money that each student had saved. The study surveyed a random sample of 97 AP students in the high school and found a mean savings of 4100 dollars with a standard deviation of 500 dollars. What would be the critical value for a 90% confidence interval in this situation?

A study by the department of education of a certain state was trying to determine the mean SAT scores of the graduating high school seniors. The study examined the scores of a random sample of 25 graduating seniors and found the mean score to be 471 with a standard deviation of 83. Which conditions for calculating a confidence interval are met for this situation? Check all that are met.

• Random Condition

• 10% Condition

• Normal/Large Sample Condition

A study by the department of education of a certain state was trying to determine the mean SAT scores of the graduating high school seniors. The study examined the scores of a random sample of 25 graduating seniors and found the mean score to be 471 with a standard deviation of 83.

What would the critical value for a 98% confidence interval be in this situation?

We measure the height of 40 randomly selected women, in which the mean height is 175cm. We also know the population standard deviation is 20cm. Which of the following represents a 95% Confidence Interval?

• 175cm ±1.645* 3.16

• 175cm ± 1.96*3.16

• 175cm ± 1.96*20

• 175cm ± 1.645*40

You sample 12 bugs and find the sample mean is 2.40 cm. You are told the standard deviation is 0.2 cm. Find a 95% Confidence Interval.

Identify the Variables

• 1.96

• μ

• .2

• n

• 12

• Z

• 2.40

• σ

You sample 16 students in your school, and they average 13 hours of TV a week. Assume the standard deviation is 3. Find a 99% Confidence Interval.

• 99% confident the population mean is between 11.77 and 14. 23

• 99% confident the population mean is between 11.53 and 14.47

• 99% confident the sample mean is between 11.06 and 14.96

• 99% confident the population mean is between 11.06 and 14.96

A random sample of 100 visitors to a popular theme park spent an average of $142 on the trip with a sample standard deviation of $47.50. Which of the following would be the 98% confidence interval for the mean money spent by all visitors to this theme park?

• 
  ($130.77, $153.23)

• 
  ($132.69, $151.31)

• 
  

  ($130.96, $153.07)

• 
  ($140.88, $143.12)

You are testing chocolate chip cookies to estimate the mean number of chips per cookie. You sample 25 cookies and you find a sample mean of 10 chips per cookie and a standard deviation of 2. Find a 95% confidence interval. Which of the following is incorrect?

• μ = 25

• σ = 2

• Z = 1.96

• n = 25

Thirty randomly selected students took the calculus final. If the sample mean was 92 and the standard deviation was 9.4, construct a 99 percent confidence interval for the mean score of all students from which the sample was gathered.

• 89.08 < μ < 94.92

• 87.27 < μ < 96.73

• 87.29 < μ < 96.71

• 87.77 < μ < 96.23