Hands-On Data Science with R

Be careful

Previously, in the Running t-tests with R section, we used the bigger sample to run a t-test; but what about the smaller sample? Speaking of R, yes, we can run it. The next code block shows how, but you shouldn't trust a sample so small:

t.test(small_sample, mu = 10, alternative = 'two.sided')#   One Sample t-test# # data: small_sample# t = -2.2169, df = 9, p-value = 0.05384# alternative hypothesis: true mean is not equal to 10# 95 percent confidence interval:#   5.043347 10.050084# sample estimates:# mean of x #  7.546716 

The test now came close to rejecting the null hypothesis with a 95% confidence level (and, as we already know, the sample does come from a normal distribution with a mean, µ, equal to 10). This test is not all mighty ...