Question

8) (1 point) A professor using an open source introductory statistics book predicts that 10% of the students will purchase a hard copy of the book, 40% will print it out from the web, and 50% 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 316 students, 14 said they bought a hard copy of the book, 137 said they printed it out from the web, and 165 said they read it online. Round all answers to four decimal places.

1. State the hypotheses for testing if the professor's predictions were inaccurate.

H0H0: The professor's predictions  ? were were not  accurate. The difference  ? is is not  due to chance.

HAHA: The professor's predictions  ? were were not  accurate. The difference  ? is is not  due to chance.

2. Enter the expected values for the hypothesis test in the table below:

Book Format	Expected Value
Hard copy
Print from web
Read online

3. Calculate the chi-squared statistic:

4. Calculate the degrees of freedom:

5. Calculate the p-value:

6. Based on the p-value, we have:
A. very strong evidence
B. some evidence
C. extremely strong evidence
D. strong evidence
E. little evidence
that the null model is not a good fit for our observed data.

Answer 1

applying chi square goodness of fit test:

	relative	observed	Expected	residual	Chi square
category	frequency(p)	Oi	Ei=total*p	R2i=(Oi-Ei)/√Ei	R2i=(Oi-Ei)2/Ei
1	0.100	14.0	31.60	-3.13	9.803
2	0.400	137.0	126.40	0.94	0.889
3	0.500	165.0	158.00	0.56	0.310
total	1.000	316	316		11.0016
test statistic X2 =		11.0016

1)H0: The professor's predictions were  accurate. The difference  is due to chance.

Ha: The professor's predictions were not accurate. The difference   is not due to chance.

2)

Book Format	Expected Value
Hard copy	31.6
Print from web	126.4
Read online	158

3)

chi-squared statistic=11.0016

4)

degree of freedom =categories-1=

2

5)

p value =0.0041

6)]

A. very strong evidence