R Question 3

Animals that are infected with a pathogen often have disturbed circadian rhythms. (A circadian rhythm is an endogenous daily cycle in a behavior or physiological trait that persists in the absence of time cues.) Shirasu-Hiza et al. (2007) wanted to know whether it was possible that the circadian timing mechanism itself could have an effect on disease. To test this idea they sampled from three groups of fruit flies: one "normal", one with a mutation in the timing gene *tim01*, and one group that had the tim01 mutant in a heterozygous state. They exposed these flies to a dangerous bacteria, *Streptococcus pneumoniae*, and measured how long the flies lived afterwards, in days. The date file "circadian mutant health.csv" shows some of their data.

Submit your R code for this question.

a. Plot a histogram of each of the three groups. Do these data match the assumptions of an ANOVA?

b. Use a Kruskal-Wallis test to ask whether lifespan differs between the three groups of flies.

(please help with how to write the right R code for this question)

genotype days_to_death

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 1

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 2

tim01 3

tim01 3

tim01 3

tim01 4

tim01 5

tim01 6

tim01 6

tim01 9

tim01 10

tim01 12

tim01 15

tim01 18

tim01 (rescued) 2

tim01 (rescued) 2

tim01 (rescued) 2

tim01 (rescued) 3

tim01 (rescued) 3

tim01 (rescued) 3

tim01 (rescued) 3

tim01 (rescued) 4

tim01 (rescued) 4

tim01 (rescued) 4

tim01 (rescued) 6

tim01 (rescued) 6

tim01 (rescued) 6

tim01 (rescued) 6

tim01 (rescued) 7

tim01 (rescued) 7

tim01 (rescued) 7

tim01 (rescued) 8

tim01 (rescued) 8

tim01 (rescued) 9

tim01 (rescued) 9

tim01 (rescued) 10

tim01 (rescued) 10

tim01 (rescued) 10

tim01 (rescued) 10

tim01 (rescued) 11

tim01 (rescued) 13

tim01 (rescued) 13

tim01 (rescued) 15

tim01 (rescued) 16

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

tim01 (rescued) 18

wild type 1

wild type 1

wild type 1

wild type 2

wild type 2

wild type 2

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wild type 5

wild type 5

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wild type 6

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wild type 10

wild type 10

wild type 14

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wild type 20

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