Thursday 3/28 Stats Do Now

Which of the following is an appropriate interpretation of a p-value?

• The probability of rejecting H₀, when we should have failed to reject H₀.
• The probability of failing to reject H₀, when we should have rejected H₀.
• Assuming H₀ is true, it is the probability of obtaining our sample statistic or a more extreme value.
• Assuming H₀ is NOT true, it is the probability of obtaining our sample statistic or a more extreme value.

How much faster do people who own sports cars drive on the freeway compared to people who own economy cars.  520 sports cars and 890 economy cars were clocked as they passed by on the freeway. Which procedure is appropriate?

• t interval for means
• t interval for difference of means
• z interval for proportions
• z interval for difference of proportions

Estimate the average number of pinecones that a 30-year-old pine tree produces each year.  Fifty-five pine trees were observed over a one-year period. Which procedure is appropriate?

• t interval for means
• t test for means
• z interval for proportions
• z test for proportions

The NCAA requires colleges to report the graduation rates of their athletes. One Big Ten university reported that the graduation rates for a specific year were 21 of 28 females athletes and 24 of 46 male athletes. Is there evidence that a smaller proportion of male athletes than of female athletes graduate?

• 1-sample t-test

• 1-sample t-test (mean difference)

• 2-sample t-test (difference in means)

• 2-proportion z-test

Failing to reject a null hypothesis that is false can be characterized as

• a Type I error
• a Type II error
• both a Type I and Type II error
• no error

A Type I error is when: 

• We reject the null hypothesis when it is actually true
• We obtain the wrong test statistic
• We fail to reject the null hypothesis when it's actually false
• We reject the alternate hypothesis when it's actually true

A hypothesis test tests the null hypothesis Ho: μ = 20 against the alternative hypothesis Ha: μ ≠ 20 at a significance level of alpha.  If the same procedure is used to test Ho: μ = 20 against Ha: μ > 20 with the same data then the p-value will

• increase
• decrease
• remain the same
• be doubled

A researcher plans to conduct a test of hypotheses at the α = 0.01 significance level.  She designs her study to have a power of 0.90 at a particular alternative value of the parameter of interest.  The probability that the researcher will commit a Type I error is

• 0.01
• 0.10
• 0.90
• 0.99

Which of the following statements is FALSE?

• The power of the test increases as α increases.
• The power of a test does not depend on the sample size.
• The power of a test is the complement of a Type II error.
• As the α-level increases, P(Type II error) decreases.

What is the best flavor of starburst?

• Yellow

• Red

• Pink

• Orange