Alternative Hypothesis

An alternative hypothesis is contrary to the null hypothesis, usually that the observations are the result of a real effect. Alternative hypothesis is the hypothesis that we actually test for in the hypothesis testing. Alternative hypothesis denoted by H1 or Ha states that there is a statistical significance between two variables. An alternative hypothesis is considered True if the Null hypothesis is proven False.

Example

Suppose we want to test the hypothesis that smokers need less sleep than the general public who need an average sleep of 7 hours. Number of smokers questioned for this hypothesis is 100. If the sample mean is 7.9 and the population standard deviation is 0.5. In this case,

Null Hypothesis H0:  mean is equal to  7

Alternative Hypothesis Ha:  mean is not equal to 7