Confidence Intervals for Means Intro

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

• 12

• 24

• 33

• None of these.

Which z-value is used for a 95% confidence interval?

• 2.58

• 1.66

• 1.96

• 2.33

Identify the confidence interval used in the figure below if each shaded area is equal to 0.05.

• 90%

• 95%

• 97%

• 99%

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

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)

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

• (89.08, 94.92)

• (87.27, 96.73)

• (87.29, 96.71)

• (87.77, 96.23)

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

A random sample of 100 visitors to a popular theme park spent an average of $142 on the trip with a standard deviation of $47.5. 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)

• ($132.77, $151.43)

• ($132.69, $151.31)

• ($140.88, $143.12)

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.

Which of the following is incorrect?

• μ = 13

• σ = 3

• Z = 1.645

• n = 16