Question

Directional and non-directional

Hello! I'm having som trouble understanding the meaning of directional and non-directional hypothesis. What does it mean, and how do this affect the p-value?

I also heard about "negative directional alternative" but could not find any information about this

Thank you!

Answer 1

Answer)

In directional hypothesis claim is either greater than or less than

While in non directional claim is either equal to or not equal to

For example

Lets say population mean is = 5

We need to test if mean has increased or not

Then hypothesis would be

Null hypothesis Ho : u = 5

Alternate hypothesis Ha : u > 5

Or if we want to test mean has decreased

Then hypothesis would be

Null hypothesis Ho : u = 5

Alternate hypothesis Ha : u < 5

The above two examples are of directional hypothesis

Now for non directional hypothesis

If we want to test if mean has been changed

Then hypothesis would be

Null hypothesis Ho : u = 5

Alternate hypothesis Ha : u not equal to 5