If a 95% confidence interval does NOT include 0, what does this imply?

A 95% confidence interval that does not include 0 indicates that the result is statistically significant. This is because the confidence interval provides a range of values within which we can be 95% confident that the true population parameter lies. If the interval excludes 0, it suggests that there is a meaningful difference or effect present in the data.

In hypothesis testing, a common null hypothesis is that there is no effect or difference, which corresponds to a value of 0. When the confidence interval excludes this value, it implies that the data observed provide strong evidence against the null hypothesis, leading to the conclusion that the results are statistically significant. This reinforces the finding that the effect observed in the study is unlikely to be due to random chance.

The other options do not accurately represent the situation when a confidence interval excludes 0. For example, a non-significant result would be indicated if the confidence interval includes 0, hence, option A is incorrect. Insufficient data would more likely lead to wide confidence intervals that may include 0, making option C inappropriate. Lastly, adjusting the hypothesis is not directly related to the significance of the findings, making option D unrelated to the interpretation of the confidence interval in question.