Stat 1040
Chapter 15 Solutions - Special Review Exercises

S1.
False because the population size increased too. We must compare rates. It turns out that the population size was 203 million in 1970 and 249 million in 1990, so the murder rate actually decreased slightly.

S3.
False - it's like the Berkeley admissions data. The pooled percentage of women admitted is
(10+18)/(79+102)*100% = 15.5%
and for men it's
(250+331)/(1312+1259)*100% = 22.6%,
so the pooled selection ratio is 15.5/22.6*100% = 68.6%.

S4.
(a) is correct. (b) has too much area and (c) has the wrong units.

S5.
About 1 year. A month would be too little variability, and 5 years would be too much.

S6.
False - these are cross-sectional data so we can not say anything about what happens to a group of people over time. Perhaps what accounts for the pattern is that the older people were less educated so they tended to be employed in less well-paid jobs.

S9.
  1. The 70th percentile is .52 in standard units, so this one scored 50+(0.52*20) = 60 points. The 80th percentile is .84 in standard units, so this one scored 50+(0.84*20) = 67 points. The brothers differed by around 7 points.
  2. About 9 points.

S12.
  1. True.
  2. True.
  3. False.
  4. False.