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Tyto alba

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**The**

__problem statement__, all variables and given/known data with__attempts__While solving problems of Goodness of fit, I'm faced with an issue, how to decide which ratio to consider to find the test statistic from given set of observations.

**E.g. 1**

*A supplied sample contains four types of seeds and the total number is 64. The types of seeds are large red 42, large white 8, small red 10 and small white 4. Calculate goodness of fit.*

Attempts & Problem: As df=3, Ratio= 9:3:3:1 / 1:1:1:1?

**E.g.2**

*You are supplied with two different varieties of plant samples;tall-76 and short-24. Determine the observed number, apply Chi square test to state whether it is in agreement with expected ratio.*

Attempts & Problem: As df=1, Ratio= 3:1 /1:1?

I was vaguely told by my professor that which ever ratio seems to apply(by logical guess) we should choose that one to determine the expected values and thus the statistic.

I couldn't find any good read in this regard, except those that are full of mistakes. I've been reading Statistic blogs to understand the concepts but they didn't cover these typical biological problems and those that did had the ratio mentioned.

I've another question in mind, from experimental result it is also likely to happen that we won't get one of the four types of seeds (give that mating is random and the progenies appeared by dihybrid crosses) so determining the actual ratio behind becomes more difficult as df = 2 =/= 3!

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