Assignment for Wednesday, February 1:


I. Read Section 2.3
II. Also read the handout Least Squares Regression Line. Be sure to fill in the details requested.

III. Do the following exercises to reinforce reading and for possible class discussion: 2.41(b), 2.42, 2.43, 2.44, 2.57,  2.59, 2.60

IV.  Turn in:

    1. Problem 1.134 (p. 95). Explain why the type of graph you have chosen is the most appropriate one.

    2. Problem 1.142 (p. 98), choosing the second option (estimated amount of oil recovered from differentoil wells).

    3. Problem 2.16 (p. 120)

    4. a. Before doing any calculations, guess each of the following. (You will not be graded on the basis of
whether or not your answers are correct for this part, just on whether or not you make a realistic attempt at guessing.)  

i. The typical number days in August when the high temperature in Austin is 100 or higher.

ii. What this number would be if the average August high temperature in Austin went up one degree.

iii. What this number would be if the average August high temperature in Austin went up two degrees.

b. August high temperatures in Austin are approximately normally distributed with mean 96.5 and standard deviation 4.5. Using this information, calculate each of the following. (Of course, as in all problems in this class, you need to explain what you are doing; final answers alone are not adequate.)

        i. The percentage of August days (and the typical number of August days) when the high temperature in Austin is 100 or higher. 

        ii. What this percentage (and typical number)would be if the average August high temperature in Austin went up one degree, but the distribution remained normal with standard deviation 4.5.

        iii. What this percentage (and typical number) would be if the average August high temperature in Austin went up two degrees, but the distribution remained normal with standard deviation 4.5.
iv. What this percentage (and typical number) would be if the average August high temperature in Austin remained 96.5, and the distribution of August high temperatures remained approximately normal, but the variability increased to the point where the standard deviation was one degree higher, that is, 5.5 instead of 4.5.

c. Briefly discuss how your answers in part (b) compare with your guesses in part (a), and what your answers to part (b) suggest about possible consequences of global warming. (Note: Some scientists think that global warming could increase temperature variability as well as average temperature.)

(Comment if you're interested: The actual distribution of high temperatures isn't quite normal, but the normal approximation gives the rough idea.  The actual distribution appears to be slightly skewed to the left. If we used this more accurate model, would the estimates in part (b) be larger or smaller?)