- 3.1 Answers vary.
- 3.2
- a) The area of a rectangle is base times height which in this
case 1 times 1.
- b) 1-0.8=0.2 or 20%.
- c) 60% of observations lie below 0.6.
- d) 50% of the observations lie between 0.25 and 0.75.
- 3.4
- a) median is B mean is C
- b) median and mean are both A
- c) median is B mean is A
- 3.7
- a) 95% of all pregnancies fall between 266-2*16= 234 and
266+2*16= 298.
- b) The shortest 2.5% of all pregnancies are less
than 266-2*16= 234 days.
- 3.12
- a) 25% of observations fall below z=-.67 (or
-.68)
- b) 40% of observations fall above z=.25 (or
.26)
- 3.14 The standard deviation for the narrow curve is
approximately 0.2. The standard deviation for the wider curve is
approximately 0.6.
- 3.18
- a) .0122
- b) 1-.0122 = .9878
- c) 1- .9616 = .0384
- d) .9878 - .0384 = .9494
- 3.22 (69.3-64)/2.7= 1.96
Using the standard normal table, this implies 2.5% of the women are
taller than the mean height of the men.
- 3.23 Mean height of young women is 64 inches. The z-score
of 64 inches for young men is (64 - 69.3)/2.8 = -1.89. The proportion of
young men shorter than 64 inches is approximately 0.0294.
- 3.25
- a) (750-534)/116= 1.86
Approximately 3.14 percent of the men scored better than 750 on the
math SAT in 2002.
- b) (750-500)/110 =2.27
Approximately 1.16 percent of women scored better than 750 on the
math SAT in 2002.