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Statistics 220, Fall 2005
Due September 7, 2005
1.10
a
The stemandleaf plot should look something like this.
59
633588
700234677889
8127
9077
107
11368
What constitutes large or small variation usually depends on the application
at hand, but an oftenused rule of thumb is: the variation tends to be large
whenever the spread of the data (the diﬀerence between the largest and smallest
observations) is large compared to a representative value. Here, “large” means
that the percentage is closer to 100% than it is to 0%. For this data, the spread
is 11  5 = 6, which constitutes 6/8 = .75, or, 75%, of the typical data value of
around 8. (The median is 7.7 and the mean is 8.1.) For most applications, this
is a large degree of variation.
b
The data isn’t particularly symmetric about any representative value. If any
thing it tends to be somewhat positively skewed — the high values go further
from the peak of than the low values do. Also, the mean is higher than the
median.
c
There aren’t any real outliers here.
d
There are four values
>
10 — you can see this either by directly checking the
data, or by counting the number of entries in the last two lines of the stemand
leaf plot, where the stems are 10 and 11, respectively.
1
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This homework help was uploaded on 01/31/2008 for the course STAT 220 taught by Professor Shalizi during the Fall '05 term at Carnegie Mellon.
 Fall '05
 Shalizi
 Statistics

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