An animal study investigated the effect of vitamin B supplement on the kidney dy

Question

An animal study investigated the effect of vitamin B supplement on the kidney dysfunction. Since lean and obese strains of Zucker rats naturally develop kidney problems, they were used to evaluate the effect of diet with vitamin B supplement on kidney weight. For each group of the rats (lean n=20, obese n=20), half were randomly assigned to receive a standard diet (Diet A) while the other half received the diet with vitamin B (Diet B). After these diets were maintained for 24 weeks, the rat’s kidney weights was measured and reported in Table 1. (?=0.01) Analyze the effect of obesity and diet on the kidney weight.

a) Determine the statistical significance of a) diet effects and; b) bodyweight effects;

b) Is there any interactions between obesity and diet effects?

Table 1. Effect of Diet on Kidney weight.

Explanation / Answer

The data is first imported into the R statistical software and the function aov is used to setup the anova model.

> tt <- read.csv("clipboard",header=TRUE,sep=" ")
> head(tt)
Obesity Diet Kidney
1 Lean A 1.62
2 Lean A 1.80
3 Lean A 1.71
4 Lean A 1.81
5 Lean A 1.47
6 Lean A 1.37
> kidney_aov <- aov(Kidney~Obesity*Diet,data=tt)
> summary(kidney_aov)
Df Sum Sq Mean Sq F value Pr(>F)
Obesity 1 9.063 9.063 238.34 < 2e-16 ***
Diet 1 0.548 0.548 14.40 0.000546 ***
Obesity:Diet 1 0.123 0.123 3.24 0.080235 .
Residuals 36 1.369 0.038   
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

a) Determine the statistical significance of a) diet effects and; b) bodyweight effects;

The variable diet effect is statistically significant as indicated by the p-value. Similarly, the p-value also indicates that the bodyweight variable is having significant effect on the kidney weight.

b) Is there any interactions between obesity and diet effects?

The interaction effect is also obtained as significant.

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