A researcher is conducting an experiment to evaluate a treatment that is expected to increase the scores for individuals in a population that is known to have a mean of μ = 80. The results will be examined using a one-tailed hypothesis test. Which of the following is the correct statement of the null hypothesis?
a. μ>80
b. μ=>80
c. μ<80
d. μ<=80

Null hypothesis is statement written about the population parameter with respect to the objective of the test and against to the alternative hypothesis.

It always contains = , ≤ , ≥ signs.

Given : A researcher is conducting an experiment to evaluate a treatment that is expected to increase the scores for individuals in a population that is known to have a mean of μ = 80.

The results will be examined using a one-tailed hypothesis test.

Alternative hypothesis must be : [tex]H_a: \mu>80[/tex]

Then, null hypothesis will be : [tex]H_0: \mu \leq80[/tex] [opposite to the alternative hypothesis.]

Hence, the correct answer is . d. μ<=80