jonesc at cshl.org
Mon May 6 13:38:35 EST 1996
In article <318A7422.37B1 at odyssee.net>, John Chan <johnchan at odyssee.net> wrote:
> I'm I student from Montreal and our biology class is experiencing fly
> crossing. My team crossed Wild males and dumpy sepia females(PxP). Then
> we crossed the offsprings and we obtained these results: 268 Wild Wild,
> 64 Wild Sepia, 76 Dumpy Wild and 17 Dumpy Sepia. The Chi-Square Test
> rejected our results (Our hypothesis for the ratio is 9:3:3:1).
> Considering the fact that there was no experiment or identifying errors,
> how can I explain the rejection of the results by the Chi-Square Test.
If you assume a 9:3:3:1 ratio is correct, what sorts of numbers would you
expect? If you anchor your estimate to the wild-type count of 268, then
you'd expect about 90 sepia, 90 dumpy, and 30 sepia,dumpy flies. You only
observed 70-85% of the sepia and dumpy flies you expected, and only about
50% of the double mutants expected. Does this suggest anything?
Chris Jones (jonesc at cshl.org)
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