Answer:
d. the current study does not provide significant evidence that the mean number of weekly hours has changed over the past year, since 8 falls inside the confidence interval.
Step-by-step explanation:
Mean was of 8 hours, test if it has changed:
At the null hypothesis, we test if it has not changed, that is, the mean is still of 8, so:
At the alternative hypothesis, we test if it has changed, that is, the mean is different of 8, so:
Using a 95% confidence interval of (7.7, 9.3), our conclusion is that:
8 is part of the confidence interval, which means that the study does not provide evidence that the mean has changed, and the correct answer is given by option d.