Question

Susan keeps track of the number of tickets sold for each play presented at The Community Theater. Within how many standard deviations of the mean do all the values fall?

137, 134, 91, 61, 150, 155, 110, 148, 90, 169, 67, 61

* 5
* 4
* 2
* 3

Answer 1

First calculate the mean. It is 114.4.
Then calculate the standard deviation. Call it sigma. I'll leave that up to you.
The number with the biggest deviation from the mean is 169, which is 54.6 away from the mean.

It looks to me like all numbers are within 2 sigma of the mean. But this means they are also within 3, 4 or 5 sigma. This is a poorly worded question in my opinion.

Answer 2

to find the mean, add up all your numbers and divide the sum by 12

To find the standard deviation proceed as follows:
1. take the difference between the mean and each data value
2. Square that difference, which means it didn't make any difference if the difference was + or -
3. Add up all those squared differences.
4. Divide that sum by N, or by (N-1), where N is the number of data values, in your case N=12
<b>You will have to check with your text, your instructor or your course outline to see which method you use.</b>

This result is called the variance,
5. take the √ of that result.

see ...
http://davidmlane.com/hyperstat/A16252.html

Answer 3

The answer is 2 i just took the quick check