Most things don’t work
A nice story in the Herald about a randomised trial of hand sanitiser dispensers in schools.
The study, published today in the journal PLoS Medicine, found absence rates at schools that installed dispensers in classrooms as part of the survey were similar at those “control” schools which did not.
There’s even a good description of the right way to do sample size calculations for a clinical trial
Beforehand, the authors believed a 20 per cent reduction in absences due to illness would be important enough to merit schools considering making hand sanitiser available, so designed the study to detect such a difference.
“Some previous studies suggested that there could be a bigger effect than that, but we wanted to be sure of detecting an effect of that size if it was there,” Dr Priest told the Herald.
That is, the study not only failed to find a benefit, it ruled out any worthwhile benefit. Either Kiwi kids are already washing their hands enough, or they didn’t use the supplied sanitiser.
My only quibble is that the story didn’t link to the open-access research paper.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »
These are the questions I’d ask…
What about the teacherrs, who you’d expect to have good hand hygeine and use the sanitiser correctly. Were they off school less?
Were there differences between schools? Teacher and school investment in the outcome etc. If the schools are going to bear the cost of sanitiser then there is an incentive to reduce the effect to avoid paying.
And was there any measure of the wellness of kids (or teachers) at school? Maybe the sick kids without the sanitiser were sent to school antyway but were healthy kids with the sanitiser i.e. they had equal attendance but a different health profile.
10 years ago
Of course, at least one newspaper had to backtrack into anecdote in their reporting:
Green Island School principal Steve Hayward said the school kept the dispensers after taking part in the 2009 research, and they believed it had reduced absences.
10 years ago
I read that as reporting about reactions to the trial (which seems appropriate) rather than using anecdote as evidence of effectiveness.
10 years ago