# Finding mean and standard deviation without given data

• March 29th 2010, 01:37 PM
kolorbynumber
Finding mean and standard deviation without given data
X | 0 1 2 3 4 5 6 7 8 9 10
p(x)|.01 .0 .01 .02 .02 .09 .07 .17 .29 .14 .18

the above set is a data set from a survey response, it is a rating scale from 0 to 10, 0 being the worst, 10 being the best.

The problem is how to find a mean and standard deviation of the ratings, when I'm not even sure of the size of the sample, or even if it IS a sample, although if it's a survey, it most likely is.

I'm wondering if I should be looking at it as a point estimator for p, or something else, I'm just confused and lost on where I should begin.
• March 29th 2010, 01:55 PM
mr fantastic
Quote:

Originally Posted by kolorbynumber
X | 0 1 2 3 4 5 6 7 8 9 10
p(x)|.01 .0 .01 .02 .02 .09 .07 .17 .29 .14 .18

the above set is a data set from a survey response, it is a rating scale from 0 to 10, 0 being the worst, 10 being the best.

The problem is how to find a mean and standard deviation of the ratings, when I'm not even sure of the size of the sample, or even if it IS a sample, although if it's a survey, it most likely is.

I'm wondering if I should be looking at it as a point estimator for p, or something else, I'm just confused and lost on where I should begin.

Your textbook or classnotes have the required formulae .... You should know that $\overline{X} = \sum_x x \cdot p(x)$ etc.