We are interested in testing whether the variance of a population is significantly more than 625. the null hypothesis for this test is a. h0: σ2 ≤ 625. b. h0: σ2 > 625. c. h0: σ2 ≥ 625. d. h0: σ2 ≤ 25.

a. H0: σ2 ≤ 625

Explanation:

In statistics, a null hypothesis is an assumption that is used to affirm or deny a particular event that is related to one or more parameters of a population or sample.  It refer tos the statement that the researcher is working to reject, is the commonly accepted fact, it is the opposite of the alternate hypothesis which is the statement the researcher is working to prove as true.

So in this case, we are trying to prove that the variance is significantly more than 625, so that would be our alternate hypothesis, therefore, the already accepted fact is that the variance is less or equal than 625, which is the null hypothesis.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong