A researcher in environmental science is conducting a study to investigate the impact of a particular herbicide on fish. He has 60 healthy fish and randomly assigns each fish to either a treatment or a control group. The fish in the treatment group showed higher levels of the indicator enzyme. Suppose a test of significance was correctly conducted and showed no statistically significant difference in average enzyme level between the fish that were exposed to the herbicide and those that were not.
a. What conclusion can the graduate student draw from these results?

Experimental research includes to divide the concerned group 'fishes' here into 'treatment' & 'control' group, to study impact of a treatment. Hypothesis test the statistical significance of propositions. Null hypothesis signifies no impact, alternate hypothesis signifies impact.

Let averages enzyme level of treatment & control be Xt & Xc

Null Hypothesis [H0] : Xt = Xc, or Xt - Xc = 0
Alternate Hypothesis [H1] : Xt ≠ Xc, or Xt - Xc ≠ 0

If hypothesis test suggests that there is no significant difference between treatment & control group enzyme level, so we reject H0 & accept H1. It implies that the herbicide has no significant impact on fishes enzymes.