Practice Quiz: Chapter 4 — TC3 MATH200 (Brown)

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(points: 2) An Internet provider charges for bandwidth according to the equation y = 35.00 + 0.005x where x is the traffic in megabytes and y is the charge in dollars. What is the mathematical term for the number “0.005” in this equation?

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	1	8	3	2	6	1	3	7	4	9
GPA, y	3.2	2.7	3.1	3.7	2.9	3.0	2.9	2.5	3.0	2.6

(a) (points: 6) 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.

(b) (points: 3) 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.

(c) 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?

scatter plot, roughly the shape of an upside-down hanging chain 3(points: 2) A scatter plot is shown at right. Estimate r by eye as “strongly positive”, “near zero”, or “strongly negative”. Briefly explain your answer.

4(points: 2) You perform a regression and your calculator returns a value of r² = 0.2. What does that tell you about the regression?

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