Question

What is the point of doing a hypothesis test if one is given data that shows there is a difference between two groups, or that there has been an increase or decrease over time?

Answer 1

When we are given a data, we get a sample not the whole population concerned. Research helps us get the data for a particular sample of the population. Hypothesis testing allows us to make inferences about the whole population based on the sample data available.

We conduct tests at different significance levels, generally 5% significance level is acceptable to make our conclusions about the population mean, proportion, difference in means statistically significant.

We apply hypothesis tests for real life problems, say a drug has to be released in the market, before it is actually released, we observe samples of differences between two groups say effects of using and not using and then apply hypothesis tests to see whether our results will be significant for the whole population as well.

We cannot make such conclusions based on the sample groups only.