6.33 Open source textbook. A professor using an open source introductory statistics book predicts that 60% of the students will purchase a hard copy of the book, 25% will print it out from the web, and 15% will read it online. At the end of the semester he asks his students to complete a survey where they indicate what format of the book they used. Of the 126 students, 71 said they bought a hard copy of the book, 30 said they printed it out from the web, and 25 said they read it online.

(a) State the hypotheses for testing if the professor's predictions were inaccurate.

(b) How many students did the professor expect to buy the book, print the book, and read the book

exclusively online?

(c) This is an appropriate setting for a chi-square test. List the conditions required for a test and verify

they are satisfied.

(d) Calculate the chi-squared statistic, the degrees of freedom associated with it, and the p-value.

(e) Based on the p-value calculated in part (d), what is the conclusion of the hypothesis test? Interpret your conclusion in this context.

6.34 Barking deer. Microhabitat factors associated with forage and bed sites of barking deer in Hainan Island, China were examined. In this region woods make up 4.8% of the land, cultivated grass plot makes up 14.7%, and deciduous forests make up 39.6%. Of the 426 sites where the deer forage, 4 were categorized as woods, 16 as cultivated grassplot, and 61 as deciduous forests. The table below summarizes these data.39

Woods Cultivated grassplot Deciduous forests Other Total 4 16 61 345426

(a) Write the hypotheses for testing if barking deer prefer to forage in cer- tain habitats over others.

(b) What type of test can we use to answer this research question?

(c) Check if the assumptions and conditions required for this test are sat-

isfied.

(d) Do these data provide convincing evidence that barking deer prefer to

forage in certain habitats over others? Conduct an appropriate hypoth- esis test to answer this research question.

A null hypothesis for a goodness-of-fit test is

H0 :p1 =0.4, p2 =0.25, p3 =0.05, p4 =0.1, p5 =0.2. The observed frequencies are: O1 = 50, O2 = 51, O3 = 14, O4 = 12, O5 = 23.

(a) Compute the expected frequencies. (b) Compute the value of 2. (Do this using the formula.)

(c) How many degrees of freedom are there? (d) What would the relevant p-value be?

show calculation w ti 84