CHAPTER 19 SOLUTIONS AND MINIPROJECT NOTES
CHAPTER 19
THE DIVERSITY OF SAMPLES FROM THE SAME POPULATION
EXERCISE SOLUTIONS
19.1
For condition 1, there exists a population (students at the college) with a fixed proportion with a certain
trait (lefthanded).
For condition 2, a random sample of students is selected.
For condition 3, the sample
size of 200 is large enough that we are indeed likely to see at least five righthanded and five lefthanded
students.
19.2
The picture is bellshaped with a mean of 0.12 and standard deviation of 0.023 (
200
)
88
)(.
12
(.
).
19.3
a.
There exists an actual population of adults, a fixed proportion of whom have fallen asleep at the wheel
in the last year (and technically, are willing to admit it when asked!).
b.
The standard deviation is the square root of (.4)(.6)/1027, or about 0.015. The interval in which about
95% of sample proportions should fall is thus about .4
±
.03, or .37 to .43, equivalent to 37% to 43%. So
the observed proportion of 37% is just covered by the interval.
c.
It would be reasonable to conclude that they differ, since 25% is very far from the interval computed
in part b.
19.4
a.
The picture is bellshaped with a mean of 0.50 and standard deviation of the square root of (0.5)
(0.5)/800 = 0.0177 or about 0.02.
b.
Yes, it would be very unlikely.
The picture does not extend that far. In fact, it is virtually impossible.
It represents a standardized score of over 10.
c.
Optimism or overconfidence. People think they are likely to be better than average on most things.
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 '08
 SEIFRIEDTHOMASJ
 Standard Deviation, 8%, 2%, 2.5%, 17.6%, 7.1 hours

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