Standard deviation larger than the mean.

I am doing physical activity reseach. A number of papers may say something like the amount of activity per day in minutes is mean 25, standard deviation 29.

Can anybody explain to me how the SD can be more than the mean please?

In my head this would mean that some people would be doing a negative amount of PA which isn't possible.

Many thanks.

I am doing physical activity reseach. A number of papers may say something like the amount of activity per day in minutes is mean 25, standard deviation 29.

Can anybody explain to me how the SD can be more than the mean please?

In my head this would mean that some people would be doing a negative amount of PA which isn't possible.

Many thanks.

The data could be skewed so a few examples with a very large value. As the variance is simply a statistic, it would be consistent with these values, but imagining it as a symmetric normal distribution would be incorrect.

Though it probably means a normal distribution (assuming mean and variance refer to a normal distribution) isnt a great fit for the data. An exponential distribution has identical mean and standard deviation values for instance, but its very different from nomal distribution. A poisson distribution is similar in that the variance is equal to the mean.

*cos many people do next to nothing and some people have physically active full time jobs so you might get a double hump (bimodal distribution) or any sort of odd shape really.

The bold refers to the distribution and not the people?

Its one of those common things where as soon as you see mean/variance (or std dev) you immediately think of a symmetric normal distribution whereas "all" distributions have these statistics. The quotes around the all is obv for cauchy ...