Missing time

It is an occupational hazard of statisticians to check columns of numbers compulsively. Thus, I noted with amusement that in the report on the Sodexo-THE University Lifestyle Survey ("Hard work, money worries ... and hopes for a bright future", 18 March), the average student's day was only 22.2 hours long. What about the other 1.8 hours?

More seriously, it is difficult enough to teach students how to display data well without their being exposed to examples such as those given in your report.

Mike Campbell, Professor of medical statistics, University of Sheffield.