Statistics, Chapter 8 Review

What is the t value associated with 90% confidence and a sample size of 15?

• 1.341
• 1.345
• 1.761
• 1.753

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 sample standard deviation of $950. Construct a 99% confidence interval for the repair cost.

• (1069.77 < μ < 2530.23)

• (1077.13 < μ < 2522.87)

• (1167.15 < μ < 2432.85)

• None of these.

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CCSS.HSS.IC.B.4

A sample of 40 people owned an average of 1.35 apple products. It is known from a previous study that the population standard deviation of apple product ownership is 0.63 products. Construct a 95% confidence interval.

• (1.11 < μ < 1.58)

• (1.15 < μ < 1.55)

• (1.19 < μ < 1.51)

• (1.09 < μ < 1.61)

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CCSS.HSS.IC.B.4

A local bank needs information concerning the savings account balances of its customers. A random sample of 13 accounts was checked. The mean balance was $686.75 with a sample standard deviation of $256.20. Find a 95% confidence interval for the true mean.

• ($513.14 < μ < $860.36)

• ($525.59 < μ < $847.91)

• ($533.27 < μ < $840.23)

• ($531.92 < μ < $841.58)

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CCSS.HSS.IC.B.4

The heights (in inches) of adult males on a small Pacific Island are believed to be Normally distributed with an unknown mean μ. The average height of a random sample of 25 adult males from the island is found to be 69.72 inches, with a known population standard deviation of σ = 4.15 inches. A 99% confidence interval for μ is...

• (67.40 < μ < 72.04)

• (67.35 < μ < 72.01)

• (67.58 < μ < 71.86)

• (68.09 < μ < 71.35)

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CCSS.HSS.IC.B.4

Thirty-five randomly selected students took the calculus final. If the sample mean was 92 and the standard deviation was 9.4, construct a 90 percent confidence interval for the mean score of all students.

• 89.08 < μ < 94.92

• 89.31 < μ < 94.69

• 87.29 < μ < 96.71

• 87.77 < μ < 96.23

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CCSS.HSS.IC.B.4

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

• 1.714
• 1.711
• 2.064
• None of these.

A research group wishes to estimate the mean amount of time (in hours) that members of a fitness center spend exercising each week. They want to estimate the mean within a margin of error of 0.5 hours with a 95% level of confidence. Previous data suggests that the standard deviation of the population is 2.2. Which of the following is the smallest sample size they could use?

• 60

• 75

• 90

• 180

A sample size of n = 64 is drawn from a population whose standard deviation is σ = 5.6.

Find the margin of error for a 99% confidence interval for µ.

• 1.799

• 1.798

• 1.803

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CCSS.HSS.IC.B.4

The football coach randomly selected ten players and timed how long each player took to perform a certain drill. The times (in minutes) were: 13.2,  5.1,  7.5,  8.0,  12.7,  7.6,  13.8,  14.5,  7.7, and 10.5.  Determine a 95 percent confidence interval for the mean time for all players.

• 12.30 < μ < 7.82
•  7.82 < μ < 12.30
• 7.72 < μ < 12.40
• 12.40 < μ < 7.72

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CCSS.HSS.IC.B.4