Stat 1040
Chapter 11 Solutions

  1. (v).

  2. Something is wrong - GPA's are between 0 and 4. Even if you always predicted 2, you would have an rms error of less than 3.12.

    1. 1.5 inches.
    2. 1.0 inches.

    1. 12
    2. 65.8 (or round to 66)
    3. 12

    1. The area to the right of 80 is the area to the right of 1.67 under the standard norma l curve, which is about 5%.
    2. New average = 65.8, new SD = 12. Standard units = 1.18. Area = 12%.

  6. The conclusion seems as though it should be correct, but it does not follow from the data because there could be confounding factors. For example, it could be that better students just spend more time on homework.

  7. Option (iii) is correct because of the regression effect. (The students who scored 75 on the math test should average a bit less than 75 on the physics test, so less than half of them will score over 75.)

  8. True. Men with 18 years of education should have blood pressure of about 122 mm, on average (using the regression method). So, his blood pressure was slightly high.