What is the Alternative Hypothesis?

Question

A study is designed to determine the effect of an office-training course on typing productivity. Fifteen typists who have not taken the course are randomly selected. The investigator assigns 20 pages of equally difficult text to be typed by each typist both before and after completing the training course.

The investigator wants to find out whether the training course has reduced the number of errors by more than 10.

Defined D=After - Before

Answer 1

Hi Temo,

Null hypothesis means literally that, nothing, as in no difference. Alternative hypothesis is the opposite. Something has changed. In this case, the alternative is a greater-than, since we are interested in greater than ten errors, but we can also have "less than" and "not equal to" alternatives.

So, if we treat a difference of 10 errors or less as negligible:

H₀ :D <= 10 (No significant difference after taking course)

H_A: D > 10 (Course significantly reduces errors)

I hope this helps.