Standard deviation of percentages

Hi,

I am trying to calculate the standard deviation of percentages. For example, if I want to look at the standard deviation of the percentage of time people spend at work on the internet, i would work out the percentage of time each person spends on the internet at work and then work out the standard deviation of these amounts.

But, as each person spends different amount of time at work, I don't know if the calculation is as simple as working out the standard deviation of the percentages I calculated. When calculating the mean, it's a simple case of weighting it based upon the number of hours each person spends at work, but not sure how any weighting, if at all, would / should be applied when calculating the standard deviation.

Thanks,

Re: Standard deviation of percentages

Do you have ANY reason to suspect the distribution is Normal? Is it even Symmetrical?

Re: Standard deviation of percentages

Normal distribution? Plotting the distribution, does show a bell type curve, but with a positive skew.