Question

This problem requires use of the MASS package installed in the previous home-

work. Do the following:

• – For the data frame birthwt in this package consider the variables bwt and smoke. Compare birth weight between smoking and non-smoking mothers by using a suitable command like boxplot.

• – Run the t-test with and without the Welch approximation to test differ- ence in means for bwt for smoking and non-smoking mothers.

Answer 1

install.packages("MASS")
library(MASS)
data(birthwt)
#a
boxplot(bwt~smoke ,data = birthwt)
#b
t.test(bwt~smoke ,data = birthwt)

0 smoke 0009 0000 00030 000 0000 bwt

> #b > t.test(bwt smoke ,data birthwt) Welch Two Sample t-test data bwt by smoke t = 2.7299, df = 170.1, p-value = 0.007003 alternative hypothesis: true difference in means is not equal to 0 95 percent confidence interval: 78.57486 488.97860 sample estimates: mean in group 0 mean in group 1 2771.919 3055.696

p-value = 0.007003 < alpha

hence there is significant difference