stat practice

A sports-and-exercise shop sampled its customer base one weekend and asked 35 customers their age. Which interval estimate of the population mean has a margin of error of 1.7 ?

•  26.0 ≤ x̄ ≤ 30.0
• 26.8 ≤ x̄ ≤ 30.2
• 33.3 ≤ x̄ ≤ 37.6
• 24.0 ≤ x̄ ≤ 46.0

Which of the following changes to a study would result in a narrower confidence interval?

• increasing the confidence level and the sample size

• decreasing the confidence level and the sample size

• increasing the confidence level, decreasing the sample size

• decreasing the confidence level, increasing the sample size.

Tags

CCSS.HSS.IC.B.4

Agricultural researchers plant 100 plots with a new variety of corn and measure the mean yield for these plots in bushels per acre. They treat the 100 plots as a simple random sample of possible plots of corn (as researchers often do) and report a 95% confidence interval for the mean corn yield of (128.4, 131.6) bushels per acre. Which of the following is a correct interpretation of the 95% confidence level?

• We are 95% confident that the true mean yield for this new variety of corn is captured by the interval (128.4, 131.6) bushels per acre
• If many intervals were constructed this way from many independent sets of 100 plots, 95% of the intervals would capture the true mean corn yield.
• If many intervals were constructed this way from many independent sets of 100 plots, 95% of the time the true mean corn yield would be in the interval (128.4, 131.6) bushels per acre.

Tags

CCSS.HSS.IC.A.1

CCSS.HSS.IC.B.4

Which of the following changes to a study would result in a narrower confidence interval?

• increasing the confidence level, increasing the sample size
• decreasing the confidence level, decreasing the sample size
• increasing the confidence level, decreasing the sample size
• decreasing the confidence level, increasing the sample size.

You have measured the systolic blood pressure of an SRS of 25 company employees. A 95% confidence interval for the mean systolic blood pressure for the employees of this company is (122, 138). Which of the following statements gives a valid interpretation of this interval?

• 95% of the sample of employees have a systolic blood pressure between 122 and 138.

• 95% of the population of employees have a systolic blood pressure between 122 and 138.

• If the procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure.

• The probability that the population mean blood pressure is between 122 and 138 is 0.95.

• If the procedure were repeated many times, 95% of the sample means would be between 122 and 138.

As sample size increases, margin of error...

• increases.

• decreases.

• stays the same.

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.

• 1.699
• 0.56
• 0.537
• 19.325

Tags

CCSS.HSS.IC.B.4

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

• 7
• 72
• 65
• 79

Tags

CCSS.HSS.IC.B.4

A sample of 20 cupcakes found the interval for calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?

• We are 95% confident that the true mean calorie content can be found with a sample of 150 to 350 cupcakes.
• We are 95% confident that the true mean calorie content in cupcakes is between 150 and 350 calories.
• We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.
• None of these are correct.

Tags

CCSS.HSS.IC.A.1

CCSS.HSS.IC.B.4

You surveyed 91 people and found that 28% of them liked Math, if the margin of error is 10.5%, what interval is likely to contain the exact percentage of all people who like Math

• 39.5<x<60.5
• 80.5<x<101.5
• 17.5<x<38.5
• 22.5<x<33.5