To study the impact of industrial waste on fish, a researcher compares the mercury levels in 15 fish caught near industrial sites to the levels in 15 of the same type of fish caught away from industrial sites. Suppose the researcher correctly conducted a test of significance. The test showed no statistically significant difference in average mercury level for the two groups of fish. What conclusion can the researcher draw from these results? The researcher must not be interpreting the results correctly; there should be a significant difference. The sample size may be too small to detect a statistically significant difference. It must be true that the industrial waste does not cause higher levels of mercury in fish.