1
Solution to Homework #1 (80 points)
Due in class9/2/2010
1. (5pts) What is the login name of your blackboard account?
2.(8pts) In a study of schizophrenia, researchers measured the activity of the enzyme monoamine
oxidase (MAO) in the blood platelets of 18 patients.
The results (expressed as nmoles
benzaldehyde product per 10
8
platelets) were as follows:
Construct a frequency distribution and display it as a table and as a histogram.
Bins
(2)
;
Frequencies
(2)
; Histogram
(2)
; Histogram labels
(2)
First decide on the bins or classes to use.
range = largest observation  smallest observation = 18.8  4.1 = 14.7
Use between 5 and 15 bins; increase the range so it divides evenly by the number of bins.
[Any number of bins from 5 to 15 is correct, but I imagine 5, 6, 8, and 10 will be common
choices, so I'll give the solutions for those.
Only one of these is required.]
Using 5 bins:
round up the range to 15.
Then bin width = range/#bins = 15/5 = 3.0.
Using 6 bins:
round up the range to 15.
Then bin width = range/#bins = 15/6 = 2.5
Using 8 bins:
round up the range to 16.
Then bin width = range/#bins = 16/8 = 2.0.
Using 10 bins:
round up the range to 15.
Then bin width = range/#bins = 15/10 = 1.5.
The starting point should be a round number
4.1.
Choose 4.0 for all #bins.
5 bins
Freq
6 bins
Freq
8 bins
Freq
10 bins
Freq
4.06.9
3
4.06.4
2
4.05.9
2
4.05.4
2
7.09.9
8
6.58.9
7
6.07.9
5
5.56.9
1
10.012.9
4
9.011.4
4
8.09.9
4
7.08.4
5
13.015.9
2
11.513.9
2
10.011.9
3
8.59.9
3
16.018.9
1
14.016.4
2
12.013.9
1
10.011.4
2
16.518.9
1
14.015.9
2
11.512.9
2
16.017.9
0
13.014.4
1
18.019.9
1
14.515.9
1
16.017.4
0
17.518.9
1
Total
18
Total
18
Total
18
Total
18
6.8
8.4
8.7
11.9
14.2
18.8
9.9
4.1
9.7
12.7
5.2
7.8
7.8
7.4
7.3
10.6
14.5
10.7
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[The end points of the bins could have more digits, e.g. 4.06.99 or 4.06.999 and still be
correct.
However, 4.07.0 would be incorrect for a bin width of 3 since that would be
overlapping.]
[Students may also give relative and/or percent frequency in their answers.
This is correct but
not necessary for full credit.]
Now draw a histogram corresponding to the frequency distribution.
[The histogram should have an overall title of something like “MAO activity in schizophenia”.
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 Fall '08
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 Standard Deviation, Interquartile range, Quartile

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