There is enough evidence to conclude that the mean number of diners changed while the free dessert offer was in effect.

Would you like more details on hypothesis testing for this conclusion? Here are some related questions to explore:

1. What types of statistical tests determine changes in a mean over time?
2. How can confidence intervals support conclusions about changes in a mean?
3. What is a null hypothesis, and how does it apply here?
4. How can p-values help determine if changes in diner count are significant?
5. What factors could affect the reliability of this conclusion?

Tip: When assessing changes over time, comparing means often involves hypothesis tests like t-tests or ANOVA to check for statistical significance.