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their appearance in a non-double-blind experiment, that such an experiment must be

considered to be fatally defective, and that no cause-effect conclusion can ever be

drawn from it with confidence.

Thus, no valid experiment exists. In short, we can be sure that no experiment has ever

been conducted to ascertain the effect of long-term alcohol consumption on longevity,

and that if such an experiment had ever been conducted, the impossibility of its being

double-blind, or even blind, would render it inconclusive.

The French Paradox Research

Must Have Been Correlational

But if the data featured in your 60 Minutes broadcast was not experimental, then what

was it? It must, by default, have been correlational. That is, rather than subjects

being assigned randomly to groups and being required to drink a given volume of alcohol

each day, it must have been merely observed what volume of alcohol they chose to drink

each day.

Alcohol consumption would be measured by self-report. Well, it is not quite true that

the experimenter would observe what volume of alcohol his subjects drank daily. It

would be impractical to follow subjects around and actually see how much alcohol they

consumed in restaurants, in bars, in their homes. Much more likely is that every once

in a long while, the subjects would be mailed a questionnaire asking them to report how

much alcohol they had been drinking lately. The inability to measure alcohol

consumption directly is already a weakness - subjects might not remember accurately how

much they had been drinking, or they might experience some pressure to distort how much

they had been drinking either upward or downward. However, this is not at all the big

weakness that I want to bring out, so let us get to that without further delay.

We have already seen that random assignment guarantees pre-treatment equality on all

dimensions. I first recapitulate that in the case of the random assignment of subjects

to groups in an experiment, we were guaranteed that the subjects in each group would be

initially equivalent on every conceivable dimension. The larger the random groups, the

closer to being precisely equal on every conceivable dimension would they become. Thus,

in a properly designed and executed double-blind experiment, any differences that

subsequently arose between groups would have to be attributed to the different

treatments that the experiment had administered to them - for example, if some groups

lived longer than others, nothing else would be able to explain this except that some

groups had consumed a different volume of wine than others.

Natural assignment guarantees pre-treatment inequality on many dimensions. But in a

correlational study, subjects are not assigned to groups randomly, they assign

themselves to groups naturally. A subject who is in a no-wine group, for example, is

one who has himself decided that he does not drink wine. Thus, the groups are referred

to not as randomly constituted, but as naturally constituted, as if nature had come

along and assigned each subject to one of the groups. Now here comes the really

important part. It is that experience teaches us that naturally-constituted groups are

capable of differing from each other on every conceivable dimension, and are highly

likely to differ from each other substantially on a number of dimensions. In other

words, people who drink no wine are likely to differ from people who drink several

glasses of wine in many ways. Perhaps the non-drinkers will have more females, and the

drinkers will have more males - or perhaps the opposite. Perhaps the drinkers will be

older or younger. Perhaps the drinkers will be richer or poorer. Perhaps the drinkers

will tend to be single and the teetotallers tend to be married, or vice versa.

Differences may readily be discovered in height, in weight, in education. Differences

could quite plausibly be discovered in smoking, in drug use, in exposure to industrial

pollutants, in diet. People who drink will tend to live in different parts of the city

from people who don't drink. People who drink may watch more television, use microwave

ovens more, spend more time breathing automobile exhaust - or less. As people of

different ethnic backgrounds, or religions, or races drink different amounts, it follows

that people who drink different amounts will differ in ethnic background, in religion,

and in race.

One can speculate about thousands of ways in which drinkers could differ from

teetotallers, and if one actually examined two such groups, one would find a few

dimensions on which such extraneous differences were large, several dimensions on which

such extraneous differences were moderate, and a large number of dimensions on which

such extraneous differences were present but small. The hurdle that the correlational

researcher is never able to overleap is that given that he is unable to look for every

conceivable difference, he will never know all the ways in which his

naturally-constituted groups did indeed differ from each other.