In a study to address whether vampire bats ( Desmodus rotundus ) in Costa Rica p

Question

In a study to address whether vampire bats (Desmodus rotundus) in Costa Rica preferentially feed on the blood of cows in estrous (in "heat"), researchers identified 350 cows that had not been attacked by bats one day, and examined the same cows the following morning for evidence of bat attacks. A total of 22 cows were in estrous, 15 of which were bitten by vampire bats. Vampire also bats bit 6 of the remaining 328 cows not in estrous.

1. How many contingency tables would report a more excessive result than the table constructed from the observed results. (I.e., maintaining the total cows either in or not in estrous, plus the number of bat attacks, how many tables would result in more bat attacks than the one observed?)

Make sure your answer is an integer

2. What would be the exact P-value for finding a one-tailed probability of at least 15 of 21 total bat attacks occurring for cows in estrous? How would this value be calculated?

P < 0.00001 ; From a Chi-square test of independence; Chi-squared statistic = 149.3906

P < 0.05 ; Based on the fact that a 95% confidence interval for the difference between proportions of attacked cows, between cows in estrous and cows not in estrous, does not bracket 0.

P = 0.2857 ; The ratio of contingency tables as extreme as the observed to the toal possible number of contingency tables

P < 0.00001 ; From a Fisher's exact test, using the hypergeometric distribution

P < 0.00001 ; From a Chi-square test of independence; Chi-squared statistic = 149.3906

P < 0.05 ; Based on the fact that a 95% confidence interval for the difference between proportions of attacked cows, between cows in estrous and cows not in estrous, does not bracket 0.

P = 0.2857 ; The ratio of contingency tables as extreme as the observed to the toal possible number of contingency tables

P < 0.00001 ; From a Fisher's exact test, using the hypergeometric distribution

Explanation / Answer

2. What would be the exact P-value for finding a one-tailed probability of at least 15 of 21 total bat attacks occurring for cows in estrous? How would this value be calculated?

P = 0.2857 ; The ratio of contingency tables as extreme as the observed to the toal possible number of contingency tables

for the other question please post it in a new question

P = 0.2857 ; The ratio of contingency tables as extreme as the observed to the toal possible number of contingency tables

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