MATH200 — Practice Quiz: Chapter 4 — 20 min

# Practice Quiz: Chapter 4

Work this like a regular quiz, using only your crib sheet. Give yourself a maximum of 20 minutes, then turn to the solutions and see how you did.

Remember, you must show your work for full credit on any problems involving computation.

1

For a random sample of TC3 students, the number of hours of TV per day and the GPA were recorded. Results were as follows:

 TV hr/day, x GPA, y 1 8 3 2 6 1 3 7 4 9 3.2 2.7 3.1 3.7 2.9 3 2.9 2.5 3 2.6

(a) (points: 2)  Make a scatter plot of these data on your calculator.

(b) (points: 3)  Find the correlation coefficient and the equation of the line that fits these points best. Round to four decimal places, and label them with their proper symbols.

(c) (points: 2)  Based on the regression, what is the expected GPA (accurate to two decimal places) for a student who watches 7 hours of TV daily? Use the proper symbol in your answer.

(d) (points: 2)  Find the value of the residual for x = 7.

(e) (points: 2)  The decision point for sample size 10 is 0.632. What if anything can you conclude about the relation between TV watching and GPA for all TC3 students?

2(points: 2)  A scatter plot is shown at right. Would the value of r be strongly positive, near zero, or strongly negative? Briefly explain your answer.

3(points: 2) Suppose you perform a regression and your calculator returns a value of R² = 0.2. What does that tell you about the regression?

Solutions to this practice quiz are available at http://www.tc3.edu/instruct/sbrown/stat/