# probability of a doz. Left-foot jandals tossed up by cyclone. (teara, Stats, Coriolis.)

Discussion in 'General Math' started by don.lotto, Jun 13, 2006.

1. ### don.lottoGuest

probability of a doz. Left-foot jandals tossed up by
cyclone. (teara, Stats, Coriolis.)

"A scientific survey of (New Zealand) beach
litter between 1974 and 1997 seems to offer
'categorical proof' of the left-footed flotsam jandal
phenomenon." (?)

Err, they must be joking!"Of the 21 jandals and shoes stumbled upon by
scientist Bruce Hayward, 70 per cent - nearly 15
footwear items - were found to be left-footed..."This is from .. click link...

a DominionPost, wellington, New Zealand piece by Lane
Nichols, 12.06.2006
www.stuff.co.nz

Indeed, project manager Jock Phillips, for NZ culture
and history online encyclopedia, said on Radio New
Zealand that "the figure is accurate."
Are you sure? CAN it be 70 per cent AND... NEARLY 15
out of 21.

Try 14 out of 21 = 2/3 ~ 67%, less than 70 %.
Try 15 out of 21 = 5/7 ~ 71.4%, more than 70%.

For a long shot, how about 14.7 / 21 = 7/10 = 70%
BINGO!
That's counting a 0.7 bit of jandal, though!

A mathematician (called my brother) replied to me that
a 70 : 30 percent proportional split of 21 Left/Right
footwear items is statistically 'so little unusual'
that it should never have been reported in an online
encyclopedia,.... teara.

Binomial discrete probability distribution, 95%
C.I.... confidence interval
= np +/- Z*sqrt(npq.)

I suspect anyone who does it that way will be as
'unreliable as margin of error.'

Pushing it further, look at 'odd versus even keno
numbers' for a remarkable contrast; instead of
left-foot vs. right-foot jandals.!

I found one-quarter of possible lucky nos picked 65%
of the numbers drawn, #3120. AT LEAST 13 out of 20
lucky numbers had [formula] 'an odd number of 10s and
odd units, e.g. 10s 30s 50s 70s.' Above.

I produced a trusty wall-chart for all such
probabilities. This one has odds of 1 in 110 thousand
and was supposed random.
(I am quite high, the 8th best mathcn I know in
Newtown.. RW WT LC JF MD DW RY.-- and I can say what I
like.)

DID X = {1 2 3 4 5 6} come up in the lottery?

A small DEC-SEPT-ION !!!, 10X +7 = 17,27,37,47,57,56.
Just 24 hrs ago, opening of teara, 12.6.06 #4168.

YES!! Pix 6/6 correct, Odds 1 : 7753 from memory.

meaning numbers are 'drawn WITHOUT REPLACEMENT.'
This is far harder to sustain a bias.

In simple language, if there had been 7 odds out of
the first 10 nos. out of the barrel, then odd numbers
are depleted, fewer odds remain. So, perhaps fewer
odds should be expected to be drawn in the second 10
nos. drawn.

odd tens and odd units.= 80*.5*.5 possible. ==20.

expected 20*20/80 = 5. Actual = 13. very rare.
Donald S. McDonald.

don.lotto, Jun 13, 2006