a. The fish whose width is 3.8 had a length of 25.5. What is the residual for this point?
b. Based on the residual plot, does a line seem like a good model for the data?Solutions to Practice Problems
Multiple-Choice
The correct answer is (c). The expected value for that cell can be found as follows:
.
The correct answer is (d). Since there are 12 months in a year, we have n = 12 and df = 12 – 1 = 11.
Reading from Table C, 0.01 < P- value < 0.02. The exact value is given by the TI-83/84 as χ 2
cdf(23.5,1000,11)=0.015.
- The correct answer is (d). Because we have independent random samples of teachers from each of
the two levels, this is a test of homogeneity of proportions. It would have been a test of independence
if there was only one sample broken into categories (correct answer would be (b) in that case). - The correct answer is (b). The expected values for the cells are exactly equal to the observed values;
e.g., for the 1st row, 1st column, , so X 2 must equal 0 the variables are
independent, and are not related.
The correct answer is (e). The expected values for this two-way table are given by the matrix:
Then,
The correct answer is (c). In a χ 2 test for independence, we are interested in whether or not two
categorical variables, measured on a single population, are related. In a χ 2 test for homogeneity of
proportions, we are interested in whether two or more populations have the same proportions for
each of the values of a single categorical variable.
- The correct answer is (e). Using Ethnicity as the row variable, there are five rows (r = 5) and four