The following is the frequency distribution for the speeds of a
sample of automobiles traveling on an interstate highway.
Speed (mph) |
Frequency |
|
50−54 |
2 |
|
55−59 |
4 |
|
60−64 |
5 |
|
65−69 |
10 |
|
70−74 |
9 |
|
75−79 |
5 |
|
35 |
The mean is 67
How to find the Variance?
Ans.
Speed(mph) | frequency(fi) | midpoint (xi) | ||
50-54 | 2 | 52 | 225 | 450 |
55-59 | 4 | 57 | 100 | 400 |
60-64 | 5 | 62 | 25 | 125 |
65-69 | 10 | 67 | 0 | 0 |
70-74 | 9 | 72 | 25 | 225 |
75-79 | 5 | 77 | 100 | 500 |
Sum = | 35 | 1700 |
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