Maintenance task times (in minutes) were observed as follows:
|
Task Time
|
Frequency
|
|
35
|
2
|
|
17
|
6
|
|
12
|
2
|
|
15
|
4
|
|
37
|
1
|
|
27
|
10
|
|
33
|
3
|
|
31
|
6
|
|
25
|
12
|
|
19
|
10
|
|
21
|
12
|
|
23
|
13
|
|
29
|
8
|
|
13
|
3
|
|
9
|
1
|
Calculate the following quantities:
a) Compute the range of the observations.
b) Assume 7 classes, with a class interval width of 4, and plot the data. Note that the resulting curve is essentially an experimental observation of the underlying probability distribution. What type of distribution does it appear to be?
c) Compute the mean repair time.
d) Compute the standard deviation of the data.
e) Assuming a normal distribution, the requirement is for a mean repair time of at most 25 minutes, with a confidence level of 95%. Is this requirement met (explain)?