Peter Niehenke (one of the best known German astrologers) in Meridian (3/1984), an astrological journal, arguing against those astrologers who think that statistical methods cannot be used to test astrology and that present science has nothing to say about it:

(my translation) Astrologers are doing statistics today and from the very start at least from that moment when they formulated the first astrological rule. Even we assume that this rule has come from 'inspiration' and not from observation: In the moment it is formulated as a rule one makes directly or indirectly a statement about frequencies. For one claims that a certain trait is more often appearing with a certain constellation thatn with others - and this way one has arrived at statistics...
One of the main objections to the use of statistical methods in astrology is over and over again the claim that it is not possible to separate the horoscope into parts and that one cannot study single constellations for this way the wholeness would be lost. This argumentation confuses two things. It is actually correct that I can never state something from a single constellation about the whole horoscope and the person...but this does not mean that one cannot study single constellations in group comparisons.

He goes on telling the example that alcohol is one factor in car accidents. This factor alone can never explain a single accident for there are many many other factors like speed, illumination, state of car, wet streets... that also play a role. So in a single case we can never be completely sure which factor or combination of factors have led to the accident. But in a groups studies with a large number of cases, the role of alcohol can be found out.

What daylia misses in her attempt to argue against using statistical methods to test astrology is that in this case the data base on which the scientists study astrology is in most cases exactly the same as the one the astrologers use: Frequencies of cooccurence of traits and constellations. If there were no pattern where from could come something like 'experience', on what basis are astrological books founded? 'Experience' ist based on seeing patterns (existing or not) and patterns can be translated into statements about frequencies. These can be tested fairly easily as TIA has said.

Niehenke, BTW, has done this and the astrological hypotheses have found no support. He has found no more significant correlations than could be expected by chance. He still does astrology in combination with psychotherapy for he finds that his clients like it and he and them have a 'feeling of evidence'.

(If astrology is done this way it may have its uses like many other methods. If a psychoanalysist talks about his client's dreams, if a cheirologist analyses hand lines or if tea leaves are read, one component that may actually be helpful is to ask the client to contribute own interpretations to the (more or less random in my eyes) pattern. Talking about one's life and trying to interpret patterns as such can be helpful in many personal crises.)

But to argue that 'experience' validates a belief and at the same time dismiss counting methods of cooccurences is intellectually dishonest. However, most astrologers are in that field for another reason. Astrologer Niehenke once more: Astrology becomes a kind of religion, a question of faith. But why not...A world in which astrology is true is a more beautiful world than a world in which astrology does not exist. That explains nicely the very emotional reaction of daylia to any alternative point of view. It is not a simple question of correct or false testable statements for her, it is a question reaching far more deep.

A scientist approaches the field very differently. It would be extremely stupid of him/her to start with the assumption that there are no patterns different from chance. Even if most of the astrological theories make no sense from a scientific point of view there could be interesting truths in astrological statements. It is simply an empirical question. (And by the way, each real scientist would hope to find a corroboration for an astrological statement for that would be much more fun and interesting than boringly 'proving' the null hypothesis)

Why would that be more interesting? The sun, obviously has a tremendous impact on humans via warmth, growth and light. The moon has a tremendous impact on some life forms via tides. It could have an influence via changes in illumination level with its phases. It even (remotely) could have a minuscule influence by its gravitation.

As for the planets, there is no serious causal influence, but nevertheless they could be correlated better than chance by spurious correlations with other more mundane influences. Birth season could play a role both for biological and for nurture reasons. The intrauterine environment could change with the season (different food), the first experiences can vary with seaons (learning to walk naked on the grass feels a bit different from learning it in lots of clothes and on snow). Different social classes have different birth frequency maxima (in Germany, the 9 months past carnival maximum is restricted to the lower classes of catholics). There is also the rumour (I've never found real data) that generals tend to be born in August and September for the simple reason that their fathers have been in the army as well and got a Christmas leave. Many interesting theories could be thought of to explain correlations of traits (or disorders) with season of birth. Knowing these things would be helpful in medicine and many other areas.

Such correlations can be found and have been found but they are not in accordance with astrological theories. The field has been tested very often but with no convincing results or with results with extremely low statistical power.

So the 'experience' and the 'feeling of evidence' must come from somewhere else: illusory correlation, Barnum effect, cold reading, retrofitting of patterns are some of the more promising interpretations where from such feelings can come in the absence of any real correlation.

Wolfgang