Tuesday, March 8, 2011

Sample size

Recently a study was published whose conclusions were that
1) if you had immediate family members with Alzheimer's Disease (AD), you had a risk of 4-10 times greater of having AD yourself
2) if that immediate family member was your mother versus your father, the risk of AD was twice as great.

Damn, while I was selecting which parent of mine should have AD, I should have gone for the dad or if given a choice, opted for the no AD parent. I am always making the wrong health decisions. See my bad choices at the Breast Cancer Store in which I apparently selected the High Risk of Recurrence Kind. Talk about buyer's remorse.

So how large of a sample is needed to jump to these conclusions and have them published in semi-reputable sources (I am reading this from the WSJ): 53 participants in which none of them had any apparent mental decline but 11 had a mom with AD and 10 had a dad with AD. All participants had their brains imaged and the ones who had parents with AD had 'shrinkage'. Furthermore, there was more shrinkage, significant shrinkage, with those with the moms with AD. Statistical significance means something very different from the layman's concept of it, a question of magnitude.

So what does this have to do with the pretty young women pictured at a wedding on the Palos Verdes peninsula outside of Los Angeles during the summer of 2006? The maid of honor is Shanna (who soon will be called a Matron of Honor). Anyway, these 5 women have since become moms of 8 boys (to be fair, one of the boys was born prior to 2006) and no girls. What are the chances of that? One in two hundred fifty-six (256 or 2 superscript 8).
Why is this so?
Palos Verdes contains an area of 'unstable' earth known as the Portuguese Bend. See above picture of the Pacific Coast Highway that is all patched up. I drove through there many years ago not long after the Northbridge Earthquake and saw this stretch with its many patchings with a sign: Caution! Unstable Earth! and was puzzled. Of course I am easily puzzled such as seeing signs on my recent drive Caution! Falling Rock Zone! What do I do with this information? Not park or build a house there? Apparently those who have ignored this sign have had their houses slide into the ocean thus the low density of houses despite its proximity to LA and the Ocean.

Could it be that exposure to this unstable ground influenced the genders of subsequent offspring? Or that 3 of these women were in my Girl Scout troop contributing to 6 of the baby boys, the lion's share, could exposure to me cause these boys? Going through Shanna's Facebook friends, there does seem to be a lot more baby boys among the former troop members.

I could write a paper on this and my conclusions, however absurd, should have the same statistical significance as the AD paper.

And if any of these wedding party members decide on a ninth baby, what are the chances it will be a boy?

One in 512?

Zero percent as it is about time for a girl to appear.

Fifty percent.

photo compliments of dk

1 comment:

Teri Bernstein said...

I like your chances of being a grandmother.


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