Tyesha found that the \( z \)-statistic was 2.1 and that the critical \( z \)-values were -1.96 and 1.96 . Which of the following is a valid conclusion based on these results? One can reject the null hypothesis. One can reject the alternate hypothesis. One can accept the null hypothesis. One cannot accept or reject the null hypothesis.

Since Tyesha's \( z \)-statistic of 2.1 falls outside the range defined by the critical \( z \)-values of -1.96 and 1.96, this means it lies in the rejection region. Therefore, one can reject the null hypothesis. In hypothesis testing, the goal is to determine if there is enough evidence against the null hypothesis. Tyesha's findings provide that evidence, allowing her to conclude that the sample data is statistically significant. So, the valid conclusion is: one can reject the null hypothesis.