AP Stat Unit 8

Another word for average is

• sample 
• mean
• data
• numerical data

To test a claim about a mean, when the population standard deviation is unknown we use:

• z procedures
• Pythagorean Theorem
• t procedures
• np > 10 and n(1-p) > 10

What does it mean when a test is statistically significant?

• it has reached alpha level status
• the test statistic had a P-value higher than the alpha level
• the test statistic had a P-value lower than the alpha level
• it is important in practical terms

A tire manufacturer claims that one particular type of tire will last at least 50,000 miles.  A group of angry customers does not believe this is so.  They take a sample of 14 tires to test if the mean mileage of the tires is really less than 50,000. 
What set of hypotheses are they interested in testing?

• a) H0: μ = 50,000 vs. Ha: μ < 50,000
• b)H0: x̅ = 50,000 vs. Ha: x̅ < 50,000
• c)H0: μ = 50,000 vs. Ha: μ ≠ 50,000
• d)H0: μ = 50,000 vs. Ha: μ > 50,000

A tire manufacturer claims that one particular type of tire will last at least 50,000 miles.  A group of angry customers does not believe this is so.  They took a sample of 14 tires to test if the mean mileage of the tires is really less than 50,000. 
If 0.0100 < P-value < 0.0200, what decision should be made if testing at the α = 0.05 level?

• a)Reject H0 and conclude that the tires were not performing as claimed.
• b)Reject H0 and conclude that the mean tire life really is 50,000 miles.
• c)Do not reject H0 and conclude that the tires were not performing as claimed.
• d)Do not reject H0 and conclude that the mean tire life really is 50,000 miles. 

Simple random samples are taken from two large populations, designated Population 1 and Population 2. Which of the following describes a situation in which the conditions for performing a two-sample t-test for the difference of two means for these populations have not been satisfied?

• n₁ = 15, n₂ = 100. The distribution of Sample 1 is symmetric and unimodal with no outliers, and the distribution of sample 2 is skewed left.
• n₁ = 15, n₂ = 15. The distributions of both samples are symmetric and unimodal with no outliers.
• n₁ = 15, n₂ = 15. The distribution of Sample 1 is symmetric and unimodal with no outliers, and the distribution of Sample 2 is skewed left with no outliers. 
• Sample size is irrelevant in
  T-procedures.

A medical researcher measured the pulse rates (beats per minute) of randomly selected adults and found the following t-based confidence interval:
With 90.00% Confidence,
71.12512 < μ(Pulse) < 73.28914
What is the correct interpretation of the t-interval? 

• A) We are 90% confident that the true, population mean of pulse rates is between 71.12512 and 73.28914 beats per minute.
• B) We are 90% confident that the true, population proportion of pulse rates is between 71.12512 and
  73.28914 beats per minute.
• C) We are 90% confident that the sample proportion of pulse rates is between 71.12512 and 73.28914
  beats per minute.
• D) We are 90% confident that the sample mean of pulse rates is between 71.12512 and 73.28914 beats
  per minute.

A medical researcher measured the pulse rates (beats per minute) of randomly selected adults and
found the following t-based confidence interval:
With 90.00% Confidence,
71.12512 < μ(Pulse) < 73.28914
What is the margin of error for this interval?

• A) 2.16402
• B)1.08201 
• C) 2
• D) 1

If a level of confidence increases from 90% to 95%, which of the 4 statements given are true?
I) The margin of error increases
II) The margin of error decreases
III) The interval width increases
IV) The interval width decreases

• A) I only
• B) II and IV
• C) I and III
• D) II and III

Researchers randomly select rats to complete at timed maze and collected 23 times (in seconds) with an average time of 55.6 second and a standard deviation of 2.3 seconds.
Which of the following statements is true?

• A) We must assume that the samples are independent.
• B) We must assume the distribution is nearly normal with no outliers because the sample size is not large enough
• C) The 10% condition is not met.
• D) The distribution is normal because the sample size is large enough.