Stat 10, UCLA
Chapter 4 Solutions
- Average=50, SD=5.
- 48, 50, 50 are within 0.5 SDs of average, that is, they fall in the
range 47.5-52.5.
48,50,50,54,57 are within 1.5 SDs of the average, that is, in the range
42.5-57.5.
-
- list (ii) has the smaller SD. (3 more entries at the average)
- list (i) (two more extreme values)
- 5, because only three of the numbers are smaller than 1, and none
are bigger than 10.
- 3, because if the SD is 1, then the entries 0.6 and 9.9 are much
too far away from the average; the SD can't be 6 because
none of the numbers are more than 6 away from the average.
- income: average would be higher
education: median would be higher
- (i) 60 (ii) 50 (iii) 40
- (i) median is bigger than average -- long left hand tail
(ii) median is about equal to the average -- symmetry
(iii) median is less than the average -- long right had tail
- 15, because most of the area is within 50 of the average, so 50 is
too big; and only a small portion of the area is within 5 of the
average, so 5 is too small.
- False. The two histograms are almost mirror images and have about
the same SD. (Remember the rule for what happens to
the SD when changing the sign of a list of numbers.)
- Average weight of men = 66*2.2 = (about) 145 pounds. SD = (about)
20 pounds. Average weight of women = (about) 121 pounds. SD = (about) 20 pounds.
- 68%. Then range is from one SD below the average to one SD above.
- Bigger than 9kg. When you combine the men and women together, the
spread increases.
-
- No. Girls must be taller than boys
- 141cm
- 163. Guess the average!
- 68%. Then range is from one SD below the average to one SD above.
- $8 (the SD=$8)
http://www.stat.ucla.edu/~dinov