I am putting together some audit results and it was suggested I present them as mean +/- SD. However there is a significant variance in the results. For example looking at hours it took to achieve a targeted temperature goal : results varied from 0 hours to 11. Using excel I ended up though with a mean of 3.73 and SD 3.6. If I were to present 2 standard deviations I thought that was meant to encompass 95% of all results however that would mean having a negative number as the lower end of the variance. This doesn't make any sense to me whatsoever as how can it possibly take negative hours to reach a goal. Is this just a statistical way of saying though there was probably temp goal achieved hours prior to protocol commencement in some cases?