Performing student's T-tests

In a Z-test, we can determine whether two mean values are significantly different if the standard deviation (or variance) is known. However, if the standard deviation is unknown and the sample size is fairly small (less than 30), we can perform a student's T-test instead. A one sample T-test allows us to test whether two means are significantly different; a two sample T-test allows us to test whether the means of two independent groups are different. In this recipe, we will discuss how to conduct a one sample T-test and a two sample T-test using R.

Getting ready

Ensure that you installed R on your operating system.

How to do it…

Perform the following steps to calculate the t-value:

1. First, we visualize a sample weight vector in a boxplot:

   > weight <- c(84.12,85.17,62.18,83.97,76.29,76.89,61.37,70.38,90.98,85.71,89.33,74.56,82.01,75.19,80.97,93.82,78.97,73.58,85.86,76.44)
   >boxplot(weight, main="A boxplot of weight")
   >abline(h=70,lwd=2, col="red")
   

   

   Figure...