According to a theory, observed frequencies of four types of a plant are in the ratio:

9/16 + θ : 3/16 - θ : 3/16 - θ : 1/16 + θ

In an experiment, observed frequencies were:

Plant A, 926
Plant B, 288
Plant C, 293
Plant D, 104

Write down the likelihood of θ given these observations. Find the maximum likelihood estimate of θ.

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How do I write down the likelihood? It sounds like it should be an easy/obvious thing, since it says "write down" and not "find". But don't I need the pdf or equivalent to do this? How do I find it from the ratio?

Any help would be much appreciated!
Thank you