How do you know whether to use mean or median when analyzing a one variable data set (box & whisker plot, i looked it up and it said to use median if its skewed right or left and mean if its symmetric, but my math teacher said something what do you guys think?

Recall that the owner of a local health food store recently started a new ad campaign to attract more business and wants to know if average daily sales have increased. historically average daily sales were approximately $2,700. the upper bound of the 95% range of likely sample means for this one-sided test is approximately $2,843.44. if the owner took a random sample of forty-five days and found that daily average sales were now $2,984, what can she conclude at the 95% confidence level?