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i have made a 3 column table for my garden data collection. The columns are: day, food given, bird seen.

Day is from 1 to 31

Food given is blank if i missed that day, or 1 if i put food out and 2 if i did not

Bird seen is blank if i missed it, 1 if i saw the bird and 2 if i did not.

How can i mathematically see if there is a link between me leaving the food out for the bird and me seeing the birds please?

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1 Answer 1

If I misunderstood and made any incorrect assumptions let me know. I think the day is not a factor so it can be used as a pairing variable. Hopefully since you only have 31 potential pairs you don't have many missing days. Now count the number of cases that are (1,1) (2,1) (1,2) and (2,2). where the first component in the score is food put out yes or no and the second is bird seen yes or no. Then construct the 2x2 table to test independence against an alternative of concordance/discordance. For your intuition if a large majority of the counts are in the (1,1) and (2,2) cells in combination you have concordance. If a large majority are in the (2,1) and (1,2) pairs then you have discordance. Otherwise you would see the concordant cell totals almost equal to the discordant cell totals indicating independence. Fisher's exact test in a 2x2 table tests for this.

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