The effect of Benzedrine on the heart rate of dogs (in beats per minute) was exa

Question

The effect of Benzedrine on the heart rate of dogs (in beats per minute) was examined in an experiment on 14 dogs chosen for the study. Each dog was to serve as its own control, with half of the dogs assigned to receive Benzedrine during the first study period and the other half assigned to receive a placebo (saline solution). All dogs were examined to determine the heart rates after 2 hours on the medication. After 2 weeks in which no medication was given, the regimens for the dogs were switched for the second study period. The dogs previously on Benzedrine were given the placebo, and the others received Benzedrine. Again, heart rates were measured after 2 hours. The following sample data are not arranged in the order in which they were taken but have been summarized by regimen. Use these data to test the research hypothesis that the distribution of heart rates for the dogs when receiving Benzedrine is shifted to the right of that for the same animals when on the placebo. Use a one-tailed Wilcoxon signed-rank test with alpha = .05.

Explanation / Answer

We shall use the open source statistical package R to solve this problem

The hypothesis formulation would be

H0 : There is no difference in the heart rates of the dogs for the placebo and benzedrine

H1 : There is a significant difference in the heart rates of the dogs for the placebo and benzedrine

Lets conduct a wilcoxon signed rank test woth alpha = 0.05 in R , also as the subjects are same this is a matched test

# read the data into R dataframe
data.df<- read.csv("C:\Users\586645\Downloads\Chegg\dog.csv",header=TRUE)
str(data.df)

wilcox.test(data.df$Placebo, data.df$Benzendrine, paired=TRUE)

> wilcox.test(data.df$Placebo, data.df$Benzendrine, paired=TRUE)

   Wilcoxon signed rank test with continuity correction

data: data.df$Placebo and data.df$Benzendrine
V = 16, p-value = 0.02365
alternative hypothesis: true location shift is not equal to 0

as the calculated p value is less than 0.05 , hence we can reject the null hypothesis in favor of alternate hypothesis and conclude that There is a significant difference in the heart rates of the dogs for the placebo and benzedrine

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