Statistics Review

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

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?

• H0: μ = 50,000 vs. Ha: μ < 50,000

• H0: x̅ = 50,000 vs. Ha: x̅ < 50,000

• H0: μ = 50,000 vs. Ha: μ ≠ 50,000

• H0: μ = 50,000 vs. Ha: μ > 50,000

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?

• We must assume that the samples are independent.

• We must assume the distribution is nearly normal with no outliers because the sample size is not large enough

• The 10% condition is not met.

• The distribution is normal because the sample size is large enough.

A graph shows the number of hours spent studying on the x-axis and the test scores on the y-axis. If the graph shows a line that slopes upwards as it moves from left to right, what does this indicate?

• As study time decreases, test scores increase.

• As study time increases, test scores decrease.

• As study time increases, test scores increase.

• There is no relationship between study time and test scores.

• A) Randomization Condition
• B) 10% Condition
• C) Independent Samples Condition
• D) Nearly Normal Distribution Condition

• A) Ho: The mean number of days 9th grade students absent is equal to the mean number of days 12th grade students are absent.
  Ha: The mean number of days 9th grade students absent is less than the mean number of days 12th grade students are absent.
• B) Ho: The mean number of days 12th grade students absent is less than the mean number of days 9th grade students are absent.
  Ha: The mean number of days 12th grade students absent is equal to the mean number of days 9th grade students are absent.
• C) Ho: The mean number of days 12th grade students absent is equal to the mean number of days 9th grade students are absent.
  Ha: The mean number of days 9th grade students absent is greater than the mean number of days 12th grade students are absent. 
• D) Ho: The mean number of days 12th grade students absent is equal to the mean number of days 9th grade students are absent.
  Ha: The mean number of days 12th grade students absent is less than the mean number of days 9th grade students are absent.

• A) Reject the Ho, so 12th grade seniors have a significantly lower mean number of absences than 9th grade freshman.
• B) Fail to reject the Ho, so 12th grade seniors have a significantly lower mean number of absences than 9th grade freshman.
• C) Reject the Ho, so there is no significant difference between 12th grade and 9th grade absences.
• D) Fail to reject the Ho, so there is no significant difference between 12th grade and 9th grade absences.

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. 

What percentage of males drive sports cars?

• 35%

• 16.25%

• 65%

• 25%