Proportions or Means Inference

A restaurant manager will randomly select a sample of filled cups each day and measure the volume of liquid in each cup. Past measurements have shown that the standard deviation of liquid dispensed by this machine is 0.2 ounces. An estimate of the mean volume must be reported within a margin of error of 0.1 ounces with 98% confidence. What is the minimum sample size for the number of drinks the manager must select?

• 2

• 5

• 16

• 17

• 22

A nutritionist claims U.S. children drink an average of less than 2 glasses of milk per day. Based on an SRS of 30 children, the p-value of H₀: μ = 2 vs. H_A: μ < 2 is 0.0015. What is the correct interpretation of the p-value?

• The probability that she fails to reject the null hypothesis is 0.015%

• The probability that she rejects the null is 0.015%

• She can be 99.85% confident that the alternative hypothesis is true

• About 0.15% of all samples would product a test statistics at least as extreme as ours if the null hypothesis is true.

• About 99.85% of all samples would product a test statistics at least as extreme as ours if the null hypothesis is true.

The process of making cough drops yields drops with varying amounts of the active ingredient. It is claimed that the average amount of this ingredient per tablet is at least 400mg. We test a random sample of 90 tablets. The mean content of the active ingredient for the sample is 396.8mg, while the standard deviation is 31mg. What is the approximate p-value for the appropriate test?

• 0.050

• 0.100

• 0.165

• 0.330

• 0.335

A major department store wants to compare the mean number of customers an employee can process per hour using two new scanning systems. 100 employees are randomly selected and then randomly assigned to one of the new systems. After each group of 50 has been trained on one scanning system and 50 on the other, the number of customers processed per hour is recorded. Which test is most appropriate for this situation?

• 1-sample t-test

• 2-sample t-test

• Paired t-test

• 1-sample z-test

• 2-sample z-test

Which of the following statements is/are true about a t-distribution with k degrees of freedom?

• I only

• II only

• I and II only

• II and III only

• I, II, and III

One- and two-sample z-procedures for sample proportions are used with ________ data.

• discrete

• continuous

• categorical

• quantitative

• subspace

Are robin eggs more likely then stellar jay eggs to hatch early during a wet spring?  Eggs of 82 robins and 75 stellar jays were observed this spring. Which procedure is appropriate?

• t test for means

• t test for difference of means

• z test for proportions

• z test for difference of proportions

Are more than 10% of households now without landline phone service?  2000 American households were surveyed. Which procedure is appropriate?

• t interval for means

• t test for means

• z interval for proportions

• z test for proportions

One- and two-sample t-procedures are used with ________ data.

• discrete

• continuous

• categorical

• quantitative

• transporter

Are people who have pets more likely to be left-handed than people who don't have pets?

• one-sample z test for a proportion

• one-sample z interval for a proportion

• two-sample z test for the difference of proportions

• two-sample z intervalfor the difference of proportions

Answer explanation

This is a yes/no question, so a test is required rather than an interval. There are two separate populations: people who have pets vs people who don't, so a two-sample test is needed.