AP Stat Inference

Hint
Check out that formula chart...again!

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Hint: remember that lovely formula chart

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Hint: did you divide first?

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Hint: For regression, you are estimating two things...how does that affect the degrees of freedom?

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Which z-value is used for a 95% confidence interval?

• 1.65

• 1.96

• 2.58

• 2.33

Construct a 95% confidence interval for the population mean, mu.  Assume the population has a normal distribution.  A sample of 25 randomly selected students has a mean test score of 81.5 with a sample standard deviation of 10.2

• (77.3, 85.7)

• (87.1, 98.3)

• (66.4, 69.9)

• (77.5, 85.5)

A student’s AP statistics project involves comparing the time it takes a student to complete a set of 25 basic trinomial factoring problems while listening to either rap music or country music. Twelve students are timed on two different sets of problems and the order of both which set of problems he does first and which music he listens to first are randomized. The resulting data is thus paired, with each student acting as his own “pair.” Which of the following conditions is required to perform a t-test on these paired data?

• The distribution of times for all students on each set of problems must be approximately Normal.

• The distribution of times for all students while listening to each type of music must be approximately Normal.

• The distribution of times for all 24 sets of problems (12 students are taking 2 tests each) must be approximately Normal.

• The distribution of differences between each individual student’s times on each of the two tests (time with rap – time with country) must be approximately Normal.

The manager of a high school cafeteria is planning to offer several new types of food for student lunches in the following school year.  She wants to know if each type of food will be equally popular so she can start ordering supplies.  To find out, she selects a random sample of 100 students and asks them, "Which type of food do you prefer: Asian food, Mexican food, pizza, or hamburgers?"  Here are the data in the table provided.  Identify the p-value and decide which of the following is the most appropriate conclusion?

• Because 0.0129 is less than α = 0.05, fail to reject H₀.  There is convincing evidence that the food choices are equally popular.

• Because 0.0129 is less than α = 0.05, reject H₀.  There is convincing evidence that the food choices are not equally popular.

• Because 0.0289 is less than α = 0.05, reject H₀.  There is convincing evidence that the food choices are not equally popular.

• Because 0.0289 is less than α = 0.05, fail to reject H₀.  There is not convincing evidence that the food choices are equally popular.

A random sample of traffic tickets given to motorists in a large city is examined.  The tickets are classified according to the race of the driver.  The results are summarized in the table provided.  The category that contributes the largest component to the χ² statistic is

• White.

• Black.

• Hispanic.

• Other.

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

• 1.341

• 1.345

• 1.761

• 1.753