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STAT 350 – Fall 2008
Lab #3  SOLUTION
Var1
–
The actual distribution of these sample points is Binomial(n = 30,
π
= 0.3)
Lab #3 – Solution
Page 1 of 5
12
10
8
6
4
9
8
7
6
5
4
3
2
1
0
var1
Frequency
Mean
8.5
StDev
2.038
N4
0
Histogram of var1
Normal
16
14
12
10
8
6
4
2
99
95
90
80
70
60
50
40
30
20
10
5
1
var1
Percent
Mean
8.5
StDev
2.038
0
AD
0.692
PValue
0.065
Probability Plot of var1
Normal  95% CI
a.
Looking just at the histogram, would you feel comfortable saying this sample came from a normal
distribution?
(
There really are no right or wrong answer – this is a judgment call, I just want you to
think about it.
)
The histogram looks a little too skewed to be normal, but aside from a little skewness, it doesn't seem all
that far from normal.
..
b.
Looking just at the probability plot (don't look at the information on the right side of the table), would
you feel comfortable saying this sample came from a normal distribution?
(
There really are no right or
wrong answer – this is a judgment call, I just want you to think about it.
)
The points are within the confidence bounds, so it seems okay.
There is an odd pattern, but that's caused by having integers.
(Notice if the distribution is Normal, but
we round to integers, we will still get this effect)
c.
According to the pvalue on the probability plot, can we say this sample came from a normal
distribution?
The
p
value is 0.065.
So that suggests the evidence is not strong enough to say this does NOT come
from a Normal distribution.
d.
If your answer to part (c) was "no", describe how the probability plot deviates from normal and compare
this to how the histogram appears to deviate from the normal.
It might help to also examine the original
data.
N/A based on my answer to (c).
Answers may vary.
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View Full Document Var2
–
The actual distribution of these sample points is Normal(
μ
= 50,
σ
= 15)
Lab #3 – Solution
Page 2 of 5
80
60
40
20
6
5
4
3
2
1
0
var2
Frequency
Mean
51.13
StDev
17.28
N1
5
Histogram of var2
Normal
120
100
80
60
40
20
0
99
95
90
80
70
60
50
40
30
20
10
5
1
var2
Percent
Mean
51.13
StDev
17.28
5
AD
0.455
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This note was uploaded on 02/23/2009 for the course STAT 350 taught by Professor Staff during the Fall '08 term at Purdue University.
 Fall '08
 Staff
 Binomial, Probability

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