Question

The dataset ’anorexia’ in the MASS package in R-Studio contains data for an anorexia study. In the study, three treat-
ments (Treat) were applied to groups of young female anorexia patients, and their weights before (Prewt) and after (Postwt)

treatment were recorded. The three treatments adminstered were no treatment (Cont), Cognitive Behavioural treatment
(CBT), and family treatment (FT).
Determine at the 5% significance level if there is a difference in mean weight gain between those receiving no treatment

and those receiving Cognitive behavioral treatment. Perform all necessary steps for the hypothesis test and interpret your re-
sults in the context of the study. Assume random selection and normal population distribution for all samples and populations.

Important: Make sure the MASS package is selected under the packages tab in R-Studio.
Useful Tip: The command subset(anorexia, Treat == "Cont")$Prewt could be used to access just the Prewt values
for subjects in the Cont treatment group.

This is the code/data I have:

> library(MASS)
> attach(anorexia)
> data=anorexia
> newdata=data[Treat=="FT",]
> newdata
Treat Prewt Postwt
56 FT 83.8 95.2
57 FT 83.3 94.3
58 FT 86.0 91.5
59 FT 82.5 91.9
60 FT 86.7 100.3
61 FT 79.6 76.7
62 FT 76.9 76.8
63 FT 94.2 101.6
64 FT 73.4 94.9
65 FT 80.5 75.2
66 FT 81.6 77.8
67 FT 82.1 95.5
68 FT 77.6 90.7
69 FT 83.5 92.5
70 FT 89.9 93.8
71 FT 86.0 91.7
72 FT 87.3 98.0
> test=t.test(data$Postwt,data$Prewt,alt="greater")
> test

Answer 1

The R output is:

The R code is:

library(MASS)
attach(anorexia)
data=anorexia
newdata=data[Treat=="FT",]
newdata
t.test(data$Postwt,data$Prewt,paired = TRUE, alternative ="two.sided")

The hypothesis being tested is:

H0: µd = 0

Ha: µd ≠ 0

p-value = 0.0044

Since the p-value (0.0044) is less than the significance level (0.05), we can reject the null hypothesis.

Therefore, we can conclude that

there is a difference in mean weight gain between those receiving no treatment and those receiving Cognitive-behavioral treatment.

Please give me a thumbs-up if this helps you out. Thank you!