The issue of presenting misleading and inaccurate information in order to support a particular viewpoint was raised on another thread about circumcision. I specifically referred to circumstitions.com as one of these sites, which prompted a response from someone who seems to have some involvement in the site.
http://www.internationalskeptics.com/forums/showthread.php?postid=3984214#post3984214
I am starting a new thread with some examples, so as not to derail the original thread.
I am using this page as an example:
http://www.circumstitions.com/HIV-SA.html
The following statements are misleading.
Research can have clinical significance (e.g. the outcome is important, the effect on that outcome is substantial) and/or statistical significance (it is very unlikely that we would see this difference if it was due to chance). Making a point of stating that the significant differences are statistical implies (otherwise why even bring it up?) that the differences are not clinically significant. Yet, by any reasonable measure (prevention of a transmissible disease with a 100% mortality, ~50% relative risk reduction, regions with double digit prevalence), the outcome is also clinically significant.
Raising this point implies that the authors are attempting to mask the size of the results. Relative risk reduction and absolute risk reduction are two different ways of summarizing information in a useful manner. That the number for relative risk is always larger than the number for absolute risk simply reflects that they are different measures, not that using one number masks information from another. If anything, the use of absolute risk reduction masks the results, because it cannot be applied to any other group when the underlying incidence varies - exactly the situation we see in spades with HIV. The authors chose to use a summary measure that was useful instead of a summary measure that was not.
No attempt is made to demonstrate that these criticisms apply or that they would negate or influence the outcome. The experiment was double-blinded to the full extent possible. Measures that were performed unblinded were objective (HIV serology) so that unblinding would be unable to affect the outcome - making the criticism irrelevant. Statistical reasons for an apparent decline in effectiveness or for the masking of a real decline in effectiveness were not applicable in this experiment. Appropriate use of statistical methods requires the selective use of statistics when considering validity and reliability.
The following statements are inaccurate:
Since the study included the promotion of safer sexual practices, it demonstrated that substantial benefit could be seen in addition to the promotion of safer sexual practices.
You can go to this site and see that there are many accepted treatments that have a higher NNT. For example, the number of people with hypertension who need to take aspirin in order to prevent one heart attack is 176, yet this is an accepted treatment. The more important consideration is the time period. You only need to circumcise men once in order to save one life per year for the next twenty years. If you want to see the same benefit in other accepted treatments, you have to treat those people twenty times. Once you inflate the NNT for accepted treatments by twenty (or reduce it for circumcision by that amount), the NNT for circumcision compares very favourably with other treatments.
These example are by no means inclusive.
Linda
http://www.internationalskeptics.com/forums/showthread.php?postid=3984214#post3984214
I am starting a new thread with some examples, so as not to derail the original thread.
I am using this page as an example:
http://www.circumstitions.com/HIV-SA.html
The following statements are misleading.
Research can have clinical significance (e.g. the outcome is important, the effect on that outcome is substantial) and/or statistical significance (it is very unlikely that we would see this difference if it was due to chance). Making a point of stating that the significant differences are statistical implies (otherwise why even bring it up?) that the differences are not clinically significant. Yet, by any reasonable measure (prevention of a transmissible disease with a 100% mortality, ~50% relative risk reduction, regions with double digit prevalence), the outcome is also clinically significant.
Raising this point implies that the authors are attempting to mask the size of the results. Relative risk reduction and absolute risk reduction are two different ways of summarizing information in a useful manner. That the number for relative risk is always larger than the number for absolute risk simply reflects that they are different measures, not that using one number masks information from another. If anything, the use of absolute risk reduction masks the results, because it cannot be applied to any other group when the underlying incidence varies - exactly the situation we see in spades with HIV. The authors chose to use a summary measure that was useful instead of a summary measure that was not.
No attempt is made to demonstrate that these criticisms apply or that they would negate or influence the outcome. The experiment was double-blinded to the full extent possible. Measures that were performed unblinded were objective (HIV serology) so that unblinding would be unable to affect the outcome - making the criticism irrelevant. Statistical reasons for an apparent decline in effectiveness or for the masking of a real decline in effectiveness were not applicable in this experiment. Appropriate use of statistical methods requires the selective use of statistics when considering validity and reliability.
The following statements are inaccurate:
Since the study included the promotion of safer sexual practices, it demonstrated that substantial benefit could be seen in addition to the promotion of safer sexual practices.
You can go to this site and see that there are many accepted treatments that have a higher NNT. For example, the number of people with hypertension who need to take aspirin in order to prevent one heart attack is 176, yet this is an accepted treatment. The more important consideration is the time period. You only need to circumcise men once in order to save one life per year for the next twenty years. If you want to see the same benefit in other accepted treatments, you have to treat those people twenty times. Once you inflate the NNT for accepted treatments by twenty (or reduce it for circumcision by that amount), the NNT for circumcision compares very favourably with other treatments.
These example are by no means inclusive.
Linda
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