Chapter 11 AP Statistics

Suppose we fit a least-squares regression line to a set of data. What is true if a plot of the residuals shows a curved pattern?

• a straight line is not a good model for the data

• the correlation must be 0

• the correlation must be positive

• outliers must be present

• The regression line might or might not be a good model for the data, depending on the extent of the curve.

All but one of the following statements contains an error. Which statement could be correct?

• There is a correlation of 0.54 between the position a football player plays and his weight.

• We found a correlation of r = –0.63 between gender and political party preference.

• The correlation between the distance travelled by a hiker and the time spent hiking is r = 0.9 meters per second.

• We found a high correlation between the height and age of children: r = 1.12.

• The correlation between mid-August soil moisture and the per-acre yield of tomatoes is r = 0.53.

The bigger the chi square statistic, the ________ the p value.

• bigger

• smaller

The table shows the number or babies born on each day of the week.  Is there evidence that births are more likely on specific days of the week?

• yes, the p value is greater than .05

• no evidence, the p value is less than .05

• yes, the p value is less than .05

• no evidence, the p value is greater than .05

The manager of a high school cafeteria is planning to offer several new types of food for student lunches in the following school year.  She wants to know if each type of food will be equally popular so she can start ordering supplies.  To find out, she selects a random sample of 100 students and asks them, "Which type of food do you prefer: Asian food, Mexican food, pizza, or hamburgers?"  Here are the data in the table provided.  Identify the p-value and decide which of the following is the most appropriate conclusion?

• Because 0.0129 is less than α = 0.05, fail to reject H₀.  There is convincing evidence that the food choices are equally popular.

• Because 0.0129 is less than α = 0.05, reject H₀.  There is convincing evidence that the food choices are not equally popular.

• Because 0.0289 is less than α = 0.05, reject H₀.  There is convincing evidence that the food choices are not equally popular.

• Because 0.0289 is less than α = 0.05, fail to reject H₀.  There is not convincing evidence that the food choices are equally popular.

Recent revenue shortfalls in a midwestern state led to a reduction in the state budget for higher education.  To offset the reduction, the largest state university proposed a 25% tuition increase.  It was determined that such an increase was needed simply to compensate for the lost support from the state.  Separate random samples of 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors from the university were asked whether they were strongly opposed to the increase, given that it was the minimum increase necessary to maintain the university's budget at current levels.  The results are in the table provided.  Why hypotheses would be appropriate for performing a chi-square test?

• The null hypothesis is that the closer students get to graduation, the less likely they are to be opposed to tuition increases.  The alternative is that how close students are to graduation makes no difference in their opinion.

• The null hypothesis is that the mean number of students who are strongly are opposed is the same for each of the 4 years.  The alternative is that the mean is different for at least 2 of the 4 years.

• The null hypothesis is that the distribution of student opinion about the proposed tuition increase is the same for each of the 4 years at the university.  The alternative is that the distribution is different for at least 2 of the 4 years.

• The null hypothesis is that year in school and student opinion about the tuition increase in the sample are independent.  The alternative is that these variables are dependent.

What is the expected value for all cells, if we assume that this is a fair six sided die?

• 96

• 16

• 8

• 1/6

In 1974, each acre of the Tahoe basin was assessed to see what condition the soil was in.  23% of acres were of type I, 32% were of type II, 41% were of type III, and 16% were of type IV.  This year the region was assessed again and the number of each type were again determined.

• Chi-square Goodness of Fit Test

• Chi-Square Test for Homogeneity

• Chi-Square Test for Independence/Association

• Not a Chi-square test

What are the degrees of freedom for the following χ² test?

• 6

• 2

• 5

• 36

A chi-square test is used to test whether a 0 to 9 spinner is "fair" (that is, the outcomes are all equally likely).  The spinner is spun 100 times, and the results are recorded.  The degrees of freedom for the test will be

• 8

• 9

• 10

• 99