Drug use at Cambridge

An article in the student newspaper “The Varsity” has just published the results of an online survey into the number of students who use illegal drugs while at Cambridge. The headline figure of 63% of students having taken illegal drugs seems very high. Headlines can be misleading however. Firstly, this does not mean that over 60% of all Cambridge students have taken drugs but only those that responded to the survey. The article does not give the number of students who completed the survey so it is impossible to gauge how prevalent drug taking might be in Cambridge. Percentage figures without an indication of the number of students who filled in the survey is misleading. If say 1000 students did the survey, of which 630 had taken drugs to give the 63% headline number, this would only be 3.5% of the total number of students at Cambridge. It cannot be assumed that the rate of drug taking will be the same between those students who completed the survey and those who did not. In surveys of this kind, there will be a bias for drug takers to want to compelete the survey. Why would students who do not take drugs be interested in completing a survey that they would see as irrelevant to them?

The second point is that the headline figure of 63% is a rather blunt instrument to convey accurately the full details of the survey. Reading the article more closely suggests that the breakdown of this headline figure is 61% marijuana, 2% cocaine and less than 1% heroin. Thus, the majority of the students who use illegal drugs are using the Class B drug, marijuana, rather than the more serious Class A drugs.