Chapter 11 - AP Stats Practice Test

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Answer explanation

The null hypothesis is a statement of equality, so H0: μ = 18. The researcher thinks that a loud

noise will cause the mice to complete the race faster, so Ha: μ < 18.

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Answer explanation

If the sample size is at least 30, we can be assured that the sampling distribution of the sample mean is

approximately Normal, therefore the t procedures are appropriate.

Tags

CCSS.HSS.ID.A.4

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Answer explanation

Because the hypothesized value, 0, is one of the plausible values in the 95% confidence interval, we fail

to reject H0: μ = 0 at the αα = 0.05 level.

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CCSS.6.SP.B.5D

CCSS.HSS.ID.A.2

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Answer explanation

Choices (d) and (e) will have the largest areas because both shade a majority of the curve. Of choices

(a) through (c), the standard Normal distribution has less area in the tail than a t distribution with df = 2

or df = 5.

P(t > 2) = tcdf(lower: 2, upper: 1000, 5) = 0.0510.

P(t > 2) = tcdf(lower: 2, upper: 1000, 2) = 0.0918.

P(z > 2) = Normalcdf(lower: 2, upper: 1000, 0, 1) = 0.0228. (smallest probability)

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CCSS.HSS.ID.A.3

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Answer explanation

Using Table B and df = 27, t = 2.051 falls between 0.025 and 0.05. Because this is a two-sided test, the

P-value falls between 0.05 and 0.10. Using technology: 2∙tcdf(lower: 2, upper: 1000, df: 27) = 0.0557.

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Answer explanation

Because the values are on a scale of 1 to 20, the populations can’t be Normal. However, the large

sample sizes justify the use of the two-sample t test. Also, the data come from independent random

samples that are both less than 10% of their respective populations.

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Answer explanation

A test for the difference between two means with population standard deviations unknown is a t test.

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CCSS.HSS.ID.A.4

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Answer explanation

With the P-value less than 0.05 we reject H0 and have convincing evidence for the alternative

hypothesis.

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CCSS.HSS.IC.B.4

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Answer explanation

For each commercial selected, there were two measurements being made. These are unlikely to be

independent because they were on the same channel at nearly the same time.

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CCSS.HSS.ID.A.4

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Answer explanation

If we are trying to detect a smaller difference, the power will be smaller because it will be harder to

detect the difference.