A Sinister Dexterity

I was trundling around the workplace today when I noticed something decidedly sinister. The clients I was serving in one section were... hmm... displaying a preponderance of left-handed behaviour. I was intrigued. Was it a purely local phenomenon? Was the cosmic order under siege? I had to know more.

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I was ruthlessly empirical about my next step. Yes, one had to design an hypothesis and gather relevant data to disprove it! (Note: data have been rounded to prevent allegations of security violation.)

Null hypothesis: there is no significant statistical difference between the proportion of left-handers in population A and that in population B. All come from the same demographics, and are indeed selected for this. Despite the fact that population A has n=250 and population B has n=100, there should be no difference in terms of proportion.

Data gathering procedure: clients were examined by visual means; this examination was then crosschecked once by observation of tool location, limb preference and digital behaviour when at rest.

Data and Data Processing:

• Population A contained 20 LH plus one ambiguous out of 250, %LH = 8%
• Population B contained 10 LH out of 90, %LH = 11.1%

This meant that the two populations had different proportions of left-handers. Ah, but was this statistically significant? How would you know?

I shall skip the subsequent steps and keep the conclusion to myself. It is safer that way.

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At this point, it might be wise, lest I be overwhelmed by sinister forces, to say that I am the direct descendant, on both sides of my family tree, of ambidextrous people. It shows to this day: I play tennis left-handed, use my left hand when gathering information, use my right hand when transcribing or writing, use my left eye when aiming and under-use my right eye. All the tests I've taken so far place me as almost (if not exactly) halfway between left-brained and right-brained orientation (if these are valid descriptors at all). For fine work I use my left hand; for crude work I use my right. I can sketch with my left hand, but my right hand is aesthetically challenged. And so on.

Readers who can identify populations A and B, please note that a certain population C comprising about 10 individuals also contained 2.5 left-handers, for a %LH of 25%. Now, assuming that the three populations A, B and C are listed in order of mathematical ability (or preference for doing mathematics at a more rarefied level), which population do you think was most mathematically inclined?

Interesting what mental activity goes on when you have an ambidextrous mind...