The most annoying health statistics are based on small study groups.
eg. 9 out of 10 dentists recommend this toothbrush. Oral B as it turns out.
In maths we call this for obvious reasons a SMALL SAMPLE SIZE. This may not be a problem when buying a toothbrush, but what if they are trying to sell you – sticking with thedentist theme – a $5,000 procedure that breaks your jaw and resets it to improve your bite?
Where are the numbers? Has there even been any research? Or a large-scale survey about this procedure? Are people happy with this procedure? Did it even work?
You do not want to make a health decision based on a study involving a SMALL SAMPLE. From the above ad, a sample of 1, dentists are a hot date. You may not want to put your faith in this statistic.
Often the alarming results of health studies published in the media are based on rats. Any study of rats gives us a insight into possible links to human health, but further studies are needed.
eg. Couch Potatoes May Be Genetically Predisposed to Being Lazy, Rat Study Suggests. The study by Frank Booth, a professor in the MU College of Veterinary Medicine was able to selectively breed rats for extreme activity or extreme laziness. They say these rats indicate that genetics could play a role in exercise motivation, even in humans.
They bred lazy rats.
They bred active rats.
They even bred rats in hats.
Rats DO NOT THINK like humans. There is no rat walking around asking ‘does my butt look big in this?
‘Even if rats experience the same disease they do not benefit from the PLACEBO EFFECT. Give a rat a sugar pill, it is just a sugar pill. But for humans a sugar pill can be 50% of the drug efficacy. Easily.
Health studies involving rats just point to an area of further research.
eg. In the 1970s rat studies suggested that artificial sweeteners caused bladder cancer. There was panic. Outrage. Hysteria. Eventually it all settled down. Further studies could not establish a link to cancer in humans. More info National Cancer Institute.
The results of rat studies are only relevant to those who hang out with lab rats namely the researchers.
There is no maths term to describe this statistical error. I’ll simply call it RATTY RESEARCH.
The doc recommends an MRI scan. A problem is identified and an operation, perhaps, recommended. But here is the problem. The back problem identified in the scan may not be the cause of the pain.
In maths this is called FALSE ATTRIBUTION.
You get all the pain – financial and physical – but no gain.
Dentists suffer a higher incidence of lower back pain … Maybe from prancing around in towels in front of mirrors. Wait. That was only a small sample of 10 paid dentists.
This may not be a problem if you are advised to, say, take more Vitamin D to correct the problem you don’t have. But if you are being advised to undergo major surgery, a second test is advisable.
False positives are common for the simple reason that if you test a million healthy people, even with a 99% accurate test, you will still have 10,000 wrong results. And that’s not including human error. Hopefully, you will not experience one of these:
The asked 8800 people about their health, lifestyle and television watching behaviour, and then followed them over the next six years, during which time 284 of them died. Among people who spent more than 4 hours a day in front of the TV, it found, the risk of their dying within the period of the study was 46 per cent higher than among those who watched less than 2 hours a day.
The error is confusing CORRELATION with CAUSATION. The risk might involve the sitting rather than TV. Or it could be that those who sit in front of TV longer are not well.
THIS IS A COMMON AND DANGEROUS ERROR INVOLVING HEALTH STATISTICS
Now that we have more screening tools we must be more cautious.
Angelia Jolie had her breasts removed because of testing positive forthe BRCA 1 and BRCA 2 genes, which are linked to an increased risk of Breast Cancer.
This is her decision. Anyone facing breast cancer would seriously consider this option.
BUT, be wary if you face this decision.
Think of Asthma. If we started our research into asthma looking for asthma genes we would have found them.
Genes create a pre-disposition for Asthma (hence the correlation) but they do not cause asthma. The dust mite, pollen, cat, dairy and other allergies cause asthma. If researchers had concentrated on genes alone our knowledge of asthma would be limited.
Another study showed that 80% of prisoners in Australia smoke. Isn’t it obvious? Smoking causes criminal behaviour!!!!!
When it comes to health stats emotions beat facts.
Not many children in Australia or the UK walk to school unsupervised or at all. The risks perceived by parents are out of proportion to the real risk. This is more to do with psychology than statistics.
It is a FAMILIARITY BIAS.
Shocking stories about car accidents and abductions terrify parents. But their fears are not supported by the numbers. As The Guardian noted, here are the stats for child pedestrian deaths in the UK.
In 2008 in England and Wales there were 1,471,100 girls aged between five and nine. The Office for National Statistics says 137 of them died from all causes. One was a pedestrian in a traffic accident. In 2010, there were no pedestrian deaths in this category.
As for abductions, the big stories capture our attention like the Madeleine McCann case. But as The Telegraph noted, more children in the UK die from window blinds (the chords are a hazard causing 4 deaths per year) than abduction.
We also tend to be more frightened by big numbers than little numbers.
In one study of this effect, people rated cancer as riskier when told that it “kills 1286 people out of 10,000” than when told it “kills 24.14 people out of 100”
approximately 156,000 people die a day. And don’t even think to look at your Star Sign. Obviously, 13,000 Geminis die each day and 13,000 Leos. And so on. For those concerned it was not their lucky day.
Too many death statistics are not good for your health either.
Tragically, independent events can cluster. One episode of Numb3rs explained this possibility very well. If you fire a machine gun at a barn wall and draw a circle around a group of bullet holes later that is a cluster. But don’t try this at home, mathspiggies.
There is a great explanation of clustering here. Some Aussie road signs show clusters of IDIOTS!
The study showed that “Men whose red meat intake put them in the top 20 per cent consumption band were 22 per cent more likely to die of cancer in the 10 years of the study, compared to men whose intake was in the lowest 20 per cent. For women, there was a 20 per cent increase in risk.”
The problem is big meat eaters tend also to be big drinkers, smokers, obese and the rest. This study has tried to separate out meat eating from other unhealthy lifestyle choices using the Cox Regression. Mathematical wizardry has produced these numbers but they don’t mean much.
If the study used a control group of drinking, smoking, obese vegans then compaing mortality rates over 10 years would be would be interesting. But where do you find half a million of them????????
Meanwhile any survey or study of a self-selecting group (eg. newspaper polls among readers) or a pre-existing group (eg. a church group, college students, yacht club, rock ‘n roll club) produces biased and therefore meaningless results.
eg. 9 out of 10 dentists who are paid to say they recommend Oral B toothbrushes is useless information, a study of paid jerks, really.
Look for a RTC or Randomised Controlled Trial.
Any study that begins a ‘trial of college students found’ (eg. psychology trials) is a BIASED SAMPLE. Look at the lifestyle of college students. How many people in the general population wear beer hats to parties? If you asked 10 beer hat wearing college students their opinion on Oral B toothbrushes they might not even recall the purpose of a toothbrush!
We are told there is an Obesity Epidemic as if you can catch obesity by standing beside someone packing a bit of cellulite.
If you have to be removed by a crane to get to hospital then you have a health problem. But obesity is presented in the media with such hysteria we could call it a NEGATIVE BIAS. The statistics are rarely questioned. And sometimes, these stats are not so damning.
Take diabetes and obesity statistics. Obesity increases the risk of diabetes. True.
According to Australian Healthy Weight Week website, an affiliate of the Dieticians Association of Australia, 61% of Australian adults are overweight. Meanwhile, the Australian Institute of Health and Welfare puts the prevalence of diabetes in Aussie adults at 4.4% (all forms). Now wrap your head around this number. Even if all the 4.4% of Aussies with diabetes were overweight (they’re not), then 92.8% of fat people in Australia don’t have diabetes. But we still think fat people are evil.
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