Mixed Inference Review

In a random sample of 1250 drivers, 450 said they would cut their driving by 10% if it helped the environment. Find a 95% confidence interval estimate of the proportion of adult drivers who are willing to cut their driving by 10%.

• (0.33, 0.39)

• (0.34, 0.38)

• (449, 450)

• (0.32, 0.40)

A counselor is interested in comparing GPAs of students with home access to internet with students who do not have internet. She randomly samples 10 students who do have internet and 10 who do not have internet and runs a t-test to compare the mean GPAs of each group. Which assumption is necessary to check?

• The population standard deviations are known

• The population standard deviations are unknown

• The population standard deviations are equal

• The population of GPA scores from each group is nearly normal

• For each sample, np and n(1-p) > 10

How does doubling the sample size change the confidence interval size in a 1-sample interval?

• Doubles the interval size

• Halves the interval size

• Multiplies the interval size by 1.414

• Divides the interval size by 1.414

• Cannot be determined without knowing the sample size

Which calculator function is used to find the critical value for a 1- or 2-proportion z-interval?

• normalcdf

• tcdf

• invNorm

• invT

A fitness center advertises that the average pulse rate of its members is 68.4 bpm. A community member suspects this is a made-up number and runs a hypothesis test on an SRS of 48 members, calculating a mean of 71 bpm and a standard deviation of 10.3. In which interval is the p-value located?

• p-value < 0.01

• 0.01 < p-value < 0.02

• 0.02 < p-value < 0.05

• 0.05 < p-value < 0.10

• p-value > 0.10

Which is true?

• Hypothesis tests are designed to measure the strength of evidence against a null hypothesis

• A well-planned hypothesis test should have a statement of either the null hypothesis is true or the null hypothesis is false

• The null hypothesis is one-sided and expressed using < or > if there is interest in deviations in only one direction

• When a true parameter value is farther from the hypothesized value, it becomes easier to reject the alternative hypothesis

• Increasing sample size makes it more difficult to conclude that an observed difference between observed values and hypothesized values is significant

A geneticist claims that four species of fruit flies should appear in the ratio 1:3:3:9. Suppose that a sample of 480 flies contained 25, 92, 68, and 295 flies of each species, respectively. What type of test is best to reject or fail to reject the geneticist's claim?

• Chi-Square Homogeneity

• Chi-Square Independence

• Chi-Square Goodness of Fit

• Difference in Means Test

• Four-proportion z-test

Two confidence intervals from the same sample are (72.2, 77.8) and (71.3, 78.7). One estimate is at the 95% confidence level, while the other is at the 99% confidence level. Which is which?

• (72.2, 77.8) is the 95% CI

• (72.2, 77.8) is the 99% CI

• Cannot be answered without knowing sample size

• Cannot be answered without knowing standard deviation

• Cannot be answered without knowing both sample size and standard deviation

A college recruiter is interested in comparing the SAT math and verbal scores of applicants at a college. A random sample of 40 applicants is chosen, and the math and verbal scores are noted. Which of the following is a proper test?

• Test of difference in two population means

• Test of difference in two population proportions

• One sample test on differences in paired data

• Chi-square goodness of fit test

• Chi-square test for homogeneity

When leaving for school, you make a judgement on the null hypothesis: The weather will stay dry. What are the results of Type 1 and Type 2 errors?

• Type 1: get drenched; Type 2: needlessly carry around an umbrella

• Type 1: needlessly carry around an umbrella; Type 2: get drenched

• Type 1: carry umbrella, it rains; Type 2: carry no umbrella, it does not rain

• Type 1: get drenched; Type 2: carry no umbrella, it does not rain

• Type 1: get drenched; Type 2: carry umbrella, it rains