Question

When testing a new​ treatment, what is the difference between statistical significance and practical​ significance? Can a treatment have statistical​ significance, but not practical​ significance?

Answer 1

Statistical significance relates to whether an effect exists.

Practical significance refers to the magnitude of the effect.

And you can have statistical significance but not practical.

Explanation:

Let's analize it with an example.

Suppose that your new treatment involves hair recovery.

You divide the population of the test in two different groups.

And you apply the treatment to only one of them.

You can see that the treatment works and there is a 3% improvment.

You have statistical significance. The treatment worked.

Now, if the test was expensive, the 3% improvement might not be practical.