When the null hypothesis is rejected, what does this indicate?

• A. There is no significant difference between groups.
• B. The test is inconclusive.
• C. The data are biased.
• D. There is a significant difference between groups.

Answer: (D)

Rejecting the null hypothesis means the observed difference between groups is unlikely to be due to random variation alone at the chosen level of significance. In other words, there is evidence of a statistically significant difference between groups. This conclusion comes from a p-value at or below the alpha threshold or a test statistic that falls into the rejection region. It’s important to note that statistical significance doesn’t imply a large or clinically important difference, and it doesn’t indicate bias in the data. An inconclusive result would be failing to reject the null, not rejecting it.