# Confirming my calculation of mean, standard deviation and median for a histogram

Average travel time* for men = 27.2 minutes, women = 23.6 minutes

My calculations are the followings:

The problem is my calculated mean is 28.4 but chart says 27.2

I calculate the mean with this formula: (sum of products of midpoint and freq) / sum of freq

• What travel time did you use for 'worked at home'? Commented Feb 10 at 2:06
• It might be that 'up to 5 minutes' includes up to 4m59s which makes 2m30s the midpoint, same for other intervals. That only gets the mean down to 28.04 though, your approximation assumes all data points in a bin are symmetric around its center, which likely doesn't hold here. Is there any reason you can't just use the reported mean? Commented Feb 10 at 6:06
• @PBulls The reason is that I want to be able to calculate it myself. So maybe they calculated the mean with the actual data, right?
– Amir
Commented Feb 10 at 16:11
• @Glen_b I didn't include it, as the chart itself also excludes it.
– Amir
Commented Feb 10 at 16:12
• The first chart shows it as the last category Commented Feb 10 at 22:51