(a) Describe a Type I and a Type II error in this setting. Which type of error could you have made in Exercise 76? Why?

(b) Which of the following changes would give the test a higher power to detect μ=120 minutes: using α=0.01 or α=0.10? Explain.

Short Answer

Expert verified

a. Type II error has been made

b. α=0.10would give the test a higher power

Step by step solution

01

Introduction

Type-I error: Rejecting the genuine invalid hypothesis or it is otherwise called misleading positive.

Type-II error: Non-rejection of a misleading invalid hypothesis or it is otherwise called bogus negative.

02

Explanation Part (a)

Type I error - Concluding that the first-year students at the university concentrate under 2.5hours of the night during the school week when they really review 2.5hours of the night during the school week.

Type-II error- Concluding that the first-year students at the university review 2.5hours of the night during the school week when they really concentrate under 2.5hours out of every night during the school week.

From the above information, a Type II error has been made.

03

Explanation Part (b)

α=0.10 would give the test a higher power as increasing the significance level maximises the power of the test.

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Most popular questions from this chapter

The most important condition for sound conclusions from statistical inference is that

(a) the data come from a well-designed random sample or randomized experiment

(b) the population distribution be exactly Normal.

(c) the data contain no outliers.

(d) the sample size be no more than 10%of the population size.

(c) the sample size be at least 30.

You are testing H0:μ=10against Hα:μ10based on an SRS of 15tobservations from a Normal population. What values of the statistic are statistically significant at theα=0.005level?

(a) t>3.326

(b) t>3.286

(c) t>2.977

(d) t<-3.326ort>3.326

(c)t<-3.286ort>3.286

A significance test allows you to reject a null hypothesis H0 in favor of an alternative Ha at the 5% significance level. What can you say about significance at the 1% level?

(a) H0 can be rejected at the 1% significance level.

(b) There is insufficient evidence to reject H0 at the 1% significance level.

c) There is sufficient evidence to accept H0 at the 1% significance level.

(d) Ha can be rejected at the 1% significance level.

(e) The answer can’t be determined from the information given

Taking stock An investor with a stock portfolio worth several hundred thousand dollars sued his broker due to the low returns he got from the portfolio at a time when the stock market did well overall. The investor’s lawyer wants to compare the broker’s performance against the market as a whole. He collects data on the broker’s returns for a random sample of36weeks. Over the 10-year period that the broker has managed portfolios, stocks in the Standard & Poor’s 500index gained an average of 0.95%per month. The Minitab output below displays descriptive statistics for these data, along

with the results of a significance test.

(a) Determine whether there are any outliers. Show your work.

(b) Interpret the P-value in context.

(c) Do these data give convincing evidence to support the lawyer’s case? Carry out a test to help you answer this question.

(a) State hypotheses for a significance test to determine whether first responders are arriving within 8 minutes of the call more often. Be sure to define the parameter of interest.

(b) Describe a Type I error and a Type II error in this setting and explain the consequences of each.

(c) Which is more serious in this setting: a Type I error or a Type II error? Justify your answer.

(d) If you sustain a life-threatening injury due to a vehicle accident, you want to receive medical treatment as quickly as possible. Which of the two significance tests—H0:μ=6.7versusHa:μ<6.7 or the one from part (a) of this exercise—would you be

more interested in? Justify your answer.

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