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Chapter 8: Q. 9.16 (page 358)

Grey-Seal Nursing. Grey seals are one of several types of ear-less seals. The length of time that a female grey seal nurses her pup is studied by S. Twiss et al. in the article "Variation in Female Grey Seal (Halichoerus grypus) Reproductive Performance Correlates to Proactive-Reactive Behavioural Types" (PLOS ONE 7(11): e49598. doi:10.1371/journal.pone.0049598). The average lactation (nursing) period of all earless seals is 23 days. A hypothesis test is to be per formed to decide whether the mean lactation period of grey seals differs from 23 days.

Short Answer

Expert verified

Part (a). 23 days

Part (b). different from 23 days

Part (c). two tailed test

Step by step solution

01

Part (a) Step 1. Given information.  

All exclusively seals have a 23-day lactation (nursing) period on average. To determine whether the mean lactation period of grey seals differs from 23 days, a hypothesis test will be conducted.

02

Part (b) Step 1. Determine the alternative hypothesis.  

Alternative hypothesis

Ha:μ≠23

Grey seal lactation period differs average of 23 days.

03

Part (c) Step 1. Classify the hypothesis test as two tailed, left tailed, or right tailed. 

Because the not equal to sign appears in the alternative hypothesis in part (b), it is evident that the hypothesis test is two-tailed.

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Most popular questions from this chapter

Calculating Power Consider a hypothesis test of the claim that the Ericsson method of gender selection is effective in increasing the likelihood of having a baby girl, so that the claim is p>0.5. Assume that a significance level of α= 0.05 is used, and the sample is a simple random sample of size n = 64.

a. Assuming that the true population proportion is 0.65, find the power of the test, which is the probability of rejecting the null hypothesis when it is false. (Hint: With a 0.05 significance level, the critical value is z = 1.645, so any test statistic in the right tail of the accompanying top graph is in the rejection region where the claim is supported. Find the sample proportion in the top graph, and use it to find the power shown in the bottom graph.)

b. Explain why the green-shaded region of the bottom graph represents the power of the test.

Estimates and Hypothesis Tests Data Set 3 “Body Temperatures” in Appendix B includes sample body temperatures. We could use methods of Chapter 7 for making an estimate, or we could use those values to test the common belief that the mean body temperature is 98.6°F. What is the difference between estimating and hypothesis testing?

Testing Hypotheses. In Exercises 13–24, assume that a simple random sample has been selected and test the given claim. Unless specified by your instructor, use either the P-value method or the critical value method for testing hypotheses. Identify the null and alternative hypotheses, test statistic, P-value (or range of P-values), or critical value(s), and state the final conclusion that addresses the original claim.

Heights of Supermodels Listed below are the heights (cm) for the simple random sample of female supermodels Lima, Bundchen, Ambrosio, Ebanks, Iman, Rubik, Kurkova, Kerr,Kroes, Swanepoel, Prinsloo, Hosk, Kloss, Robinson, Heatherton, and Refaeli. Use a 0.01 significance level to test the claim that supermodels have heights with a mean that is greater than the mean height of 162 cm for women in the general population. Given that there are only 16 heights represented, can we really conclude that supermodels are taller than the typical woman?

178 177 176 174 175 178 175 178 178 177 180 176 180 178 180 176

Test Statistics. In Exercises 13–16, refer to the exercise identified and find the value of the test statistic. (Refer to Table 8-2 on page 362 to select the correct expression for evaluating the test statistic.)

16. Exercise 8 “Pulse Rates”

In Exercises 1–4, use these results from a USA Today survey in which 510 people chose to respond to this question that was posted on the USA Today website: “Should Americans replace passwords with biometric security (fingerprints, etc)?” Among the respondents, 53% said “yes.” We want to test the claim that more than half of the population believes that passwords should be replaced with biometric security.

Equivalence of Methods If we use the same significance level to conduct the hypothesis test using the P-value method, the critical value method, and a confidence interval, which method is not equivalent to the other two?
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