#Exercise 2:  two-sample t-test and confidence interval

 

#At the lectures we looked an example on bone mineral density (cf. slide 25 from the lectures)

#We will in this exercise see how the computations for this example may be done in R.

 

 

#Start by reading the data into R. This may be done by the command:

cont=c(0.228, 0.207, 0.234, 0.220, 0.217, 0.228, 0.209, 0.221, 0.204, 0.220, 0.203, 0.219, 0.218, 0.245, 0.210)

treat=c(0.250, 0.237, 0.217, 0.206, 0.247, 0.228, 0.245, 0.232, 0.267, 0.261, 0.221, 0.219, 0.232, 0.209, 0.255)

 

# Find the means and standard deviations, and check that you get the same results as in the lectures (slide 25)

 

# Use the command "t.test" to compute the confidence interval, t-statistic and P-value:

t.test(treat, cont , var.equal=T)

 

# Make sure that you understand the output from the command and check that you get the same results as in the lectures (slides 27 and 28)

 

 

# Optional: Use the formulas given on slide 26 to compute the pooled standard deviation, the standard error of the effect of treatment, and the 95% confidence interval.

 

# Optional: Use the formulas given on slide 28 to compute the t-statistic and the P-value.