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Stating hypotheses State the appropriate null and alternative hypotheses in each of the following settings. Explain why the sample data give some evidence for Ha in each case.

a. The average height of 18-year-old American women is 64.2 inches. You wonder whether the mean height of this year’s female graduates from a large local high school differs from the national average. You measure an SRS of 48 female graduates and find that x=63.5 inches and sx=3.7 inches.

b. Rob once read that one-quarter of all people have played/danced in the rain at some point in their lives. His friend Justin thinks that the proportion is higher than 0.25 for their high school. To settle their dispute, they ask a random sample of 80 students in their school and find out that 28 have played/danced in the rain.

Short Answer

Expert verified

Part (a)H0:μ=64.2H1:μ≠64.2

Part (b) H0:p=0.25H1:p>0.25

Although the sample proportion is 0.35 which is higher than 0.25 the sample proportion is giving some evidence for H1

Step by step solution

01

Part (a) Step 1: Given information

The claim is mean differs from 64.2

02

Part (a) Step2: Calculation

The null hypothesis asserts that the population value should be the same as the claim value.

H0:μ=64.2

Either the null hypothesis or the alternative hypothesis is the assertion. The null hypothesis asserts that the population means should be the same as the claim value. If the claim is the null hypothesis, the alternative hypothesis statement is the polar opposite of the claim.

H1:μ≠64.2

Although the sample mean of 63.5differs from the hypothesized mean of 64.2 there is some indication of H1 in the sample averages.

03

Part (b) Step 1: Calculation

The null hypothesis asserts that the population value should be the same as the claim value.

H0:p=0.25

Either the null hypothesis or the alternative hypothesis is the assertion. The null hypothesis asserts that the population proportion should be the same as the claim value. If the claim is the null hypothesis, the alternative hypothesis statement is the polar opposite of the claim.

H1:p>0.25

Here, p is the percentage of pupils in that school who have played in the rain.

x=28n=80p^=xn=2880=0.35

Despite the fact that the sample proportion is 0.35which is greater than 0.25the sample proportion supports H1

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Most popular questions from this chapter

Candy! A machine is supposed to fill bags with an average of 19.2 ounces of candy. The manager of the candy factory wants to be sure that the machine does not consistently underfill or overfill the bags. So the manager plans to conduct a significance test at the α=0.10significance level of

H0:μ=19.2Ha:μnotequalto19.2

where μ=the true mean amount of candy (in ounces) that the machine put in all bags filled that day. The manager takes a random sample of 75 bags of candy produced that day and weighs each bag. Check if the conditions for performing the test are met.

Pressing pills A drug manufacturer forms tablets by compressing a granular material that contains the active ingredient and various fillers. The hardness of a sample from each batch of tablets produced is measured to control the compression process. The target value for the hardness is μ=11.5The hardness data for a random sample of 20 tablets from one large batch are

Is there convincing evidence at the 5%level that the mean hardness of the tablets in this batch differs from the target value?

Calculations and conclusions Refer to Exercise R9.1. Find the standardized test statistic and P-value in each setting, and make an appropriate conclusion.

Attitudes Refer to Exercise 4. In the study of older students’ attitudes, the sample mean SSHA score was 125.7 and the sample standard deviation was 29.8. A significance test yields a P-value of 0.0101.

a. Explain what it would mean for the null hypothesis to be true in this setting.

b. Interpret the P-value.

No homework? Refer to Exercise 1. The math teachers inspect the

homework assignments from a random sample of 50 students at the school. Only 68% of the students completed their math homework. A significance test yields a P-value of 0.1265.

a. Explain what it would mean for the null hypothesis to be true in this setting.

b. Interpret the P-value.

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