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Beverly Anderson
Section 2, Mon 1:25
30 August 2010
1.
a.
> leaves = read.table("leaves.txt")
2.
a. > head(leaves)
V1
1
61
2
75
3
79
4
68
5
79
6
66
b.
> mean(leaves)
V1
67.97727
c. > var(leaves)
V1
V1
188.2056
d. > sqrt(var(leaves))
V1
V1
13.71880
e. > mean(leaves$V1)
[1] 67.97727
3.
a. hist(leaves$V1)
Histogram of leaves$V1
leaves$V1
Frequency
20
40
60
80
100
0
5
10
15
20
25
30
35
b. > median(leaves$V1)
[1] 68
c. The mean leaf length is 67.97727mm, though the median leaf length is 68mm. Since the
histogram is in a “bellcurve” form, it is expected that the mean and median would be very close.
This is because there are about as many leaves longer than the average length as there are leaves
that are shorter than the average. Further, the bellcurve shape tells us that the distribution is
similar on both the longer end and shorter end.
d.
About 99% of the data should fall within the range of the mean – 3*standard
deviation and the mean + 3*standard deviation.
The standard deviation is
13.71880mm,
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 Fall '10
 DiSalvo

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