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Statistics 101
Homework 1 Solution
1. For the incomes of households in the United States, I would expect that the mean be larger. If you
have a few outliers (a few extremely rich families), the mean would be greatly aﬀected. The median,
however, does not take into account the magnitude of each datapoint; it looks at the set as a whole
and takes the middle value.
2.
(a) The percentages do not add up to 100
(b) The size of each wedge does not correspond to its percentage.
(c) The chart does not take into account that students may be addicted to more than one of these
groups.
No, a pie chart is not appropriate because the data is not discrete (high school students may be addicted
to many categories).
3.
(a) The mean
m
= (65+65+60+50+50+45+60+60+120+35+45+135+60+60+70)
/
15 = 65
.
33.
The standard deviation
sd
=
v
u
u
t
1
n
n
X
1
(
x
i

m
)
2
= 26
.
10. If you divide by
n

1 instead of
n
, then
the answer should be 27
.
02. The data in ascending order looks like: 35 45 45 50 50 60 60 60 60
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 Fall '08
 Heller
 Statistics

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