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Chapter 7 – Solutions for selected problems
7.4
a) The population distribution is the set of all
x
values for the population of people who suffer
occasionally from migraine headaches, 60% of which are 1 (person gets some relief from
taking ibuprofen) and 40% of which are 0 (no relief). P(0) = 0.40, P(1) = 0.60.
b) Mean=
p
=0.60.
c) Standard error=
d) The standard error describes how much the sample proportion varies from one sample (of size
24) to the next. Since the sampling distribution is approximately normal, most of the sample
proportions will fall within 3(0.10)=0.3 of the mean (0.60).
7.6
a) The interval of values within the sample proportion will almost certainly fall within three
standard errors of the mean: 0.53 to 0.59.
b) Based on the interval calculated in (a), it would be unusual to observe a sample proportion of
0.60.
c)
.
Since 0.565 falls 0.63 standard deviations above the mean, it would
not be unusual to observe a sample proportion of 0.565.
7.18
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 Spring '08
 Staff
 Statistics

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