Stat 10, UCLA
Chapter 3 Solutions

  1. 66 and 72.
    2. Note: Using our density scale, your y-axis should be labeled as this one times 100 (0, .5, 1.0, 1.5).
    1. There are more children age 1, because the histogram is higher there.
    2. There are more at 31.
    3. There are more age 35-44, that block has larger area.
    4. 50%

    1. 25%
    2. 99%
    3. 140-150 mm
    4. 135-140 mm
    5. About 10.5% (= 5 * 2.1%)
    6. 102-103 mm
    7. One of the millimeters between 115 and 120, say 117--118.

  4. 10%
  5. Lists (i) and (ii) but not (iii).

    1. true
    2. true
    3. people under 2 may round up; people just over 2 may round down.

    7. See the note above the problem 2 histogram.
    1. Last Digit of Age Histograms
    2. In 1880, people did not know their ages accurately and probably rounded off.
    3. In 1970, however, people knew better when they were born.
    4. In 1880 there seemed to be a stronger preference for even digits (except for the ever-popular 5). This is probably due to rounding. In 1970 the preference was weak.

  8. 15 people are found separated from the rest with scores above 90. The gap in the histogram just below these people is curious.

  9. False: most days of year are between 70 and 100 degrees where this peak in the histogram occurs.


http://www.stat.ucla.edu/~dinov