Adam Smith: Cause or coincidence? TV3's mistreatment of a serious issueSave
By Adam Smith
Generally, people are not very good at evaluating evidence from everyday observations. We often see patterns that aren't there and jump to conclusions. Apparently, this now passes as investigative journalism for TV3, whose 3D program gave the very delicate issue of vaccine safety a disastrous treatment on Monday night.
Let me illustrate my point about conclusion jumping with a toy example. Say, you get a new cat. Shortly thereafter, you develop a rare disease named Possibly Cat Disease (PCD). Because the PCD happened after you got a cat, it might occur to you that the cat caused your disease, because that was a recent, noticeable change in your life. This conclusion might be true, but it might not be.
To find out, you might seek scientific studies that have looked into this alleged link between cats and PCD. Scientists carefully collected data from lots of people with and without cats, and compared the rate of PCD between the two groups. If PCD occurred significantly more often among the cat owners, you have evidence for a link between cat ownership and PCD. (Note, this is still not evidence that cats cause PCD per se - just that they are associated. The association could be caused by something else, like having catfood in your house. Establishing cause requires further science).
On the other hand, you might instead ask around your community and discover that a few people with cats have PCD. You might then do some 'research' online and find anti-cat websites and videos showing hundreds of people that contracting PCD after getting a cat. You may talk to grieving mothers who resolutely blame their cat for their child's tragically fatal case of PCD.
However, this does not constitute evidence. What if, for all the hundreds of cat owners with PCD, there were thousands of non-cat owners with PCD? Real evidence comes from comparing rates of the disease among cat owners and non-cat owners. For the comparison to be valid, the data need to be collected using a scientifically robust method. Looking only at anecdotes of cat-then-PCD can tell us very little.
3D's 22-minute piece, entitled Cause or Coincidence, focused on four unfortunate young women with crippling diseases, and two who had died. They, like thousands of other girls in NZ, have had the human papillomavirus (HPV) vaccine, which reduces the risk of cervical cancer.
The majority of the piece is taken up with Paula Penfold interviewing the girls and their families.
It was shocking and sad, in more ways than one. When asked, some of the girls and parents were convinced that the vaccine was the cause, though some, to their credit, were not. Either way, as much as we feel for them, they are not in a good position to make that judgement. Regardless, Paula Penfold seemed very intent on obtaining these emotive sound bites.
The science, on the other hand, barely got a mention.