Question

Vampire bats are a model group for understanding social behaviours, altruism and "morality". This is because they share blood meal (by regurgitating some of the blood they consumed) with other bats who were not able to feed that night. This is important because if a bat misses as little as two nights worth of dinners they starve to death. Bats that have shared a meal with another bat recently are more likely to be helped in return. A researcher is interested in whether vampire bats help family or friends at different rates. They observed blood meal sharing in an experimental colony of bats where all individuals are tagged and all familial relationships are known. Each day a small number of bats are denied a meal so that they will make requests for food from other bats. The researchers tracked 9 fed bats through three months and report the number of times each of these bats shared a meal with 1) direct relatives (DR: parent, sibling, offspring) or 2) non-related bats (NR: everyone else). The data are shown below. The first entry represents the number of times one individual fed either direct relatives vs non-relatives (i.e., 10 and 8 correspond to the SAME bat). DR<-c(10, 4, 5, 11, 8, 6, 9, 3, 2) NR <-c(8, 3, 6, 8, 6, 3, 8, 1,3) 1. (2pts) Is the data dependent or independent and why? 2. (3pts) How many bats shared more with relatives? How many bats shared more with non- relatives? Are some bats much more generous than others? 3. (1pts) Is the difference in helping rates normally distributed? Provide evidence from the results of the shapiro-wilk test.

Answer 1

a)

	Direct Relatives	Non related Bats	Total
vampire 1	10	8	18
vampre 2	4	3	7
vampire 3	5	6	11
vampire 4	11	8	19
vampire 5	8	6	14
vampire 6	6	3	9
vampire 7	9	8	17
vampire 8	3	1	4
vampire 9	2	3	5

Total

58

46

104

To be independent both should have similar distributions.

Taking vampire 1 to determine whether it is independent or not.

Probability to feed direct relatives = 10/18 = 0.55

Probability to feed non related bats = 8/18 = 0.44

Taking vampire 2 to determine whether it is independent or not.

Probability to feed direct relatives = 4/7 = 0.57

Probability to feed non related bats = 3/7 = 0.42

Hence the data is independent.

(As you haven't mention which question to be answered i am only giving answer to this question)