random sample...what to conclude?

A soft drink distributor claims that a new display, featuring a life-size picture of Babe Ruth, will increase product sales in supermarkets by an average of 50 cases in a week.  For a random sample of twenty supermarkets, the average sales increase was 41.3 cases, and varied across supermarkets by about 12.2 cases.  What managerial conclusion can you draw from this data?

What do I do here?  We have only tlked about a few techniques in class from which to choose....

Techniques and possible representative applications:
-Confidence intervals and hypothesis testing
-Decision trees (and their use in solving managerial problems),
-Critical fractile analysis (and its use in determining optimal demand levels),
-Analysis of variance/ANOVA (and its use in understanding differences between group means),
-Chi-square (cross tabs/contingency table) analysis (and its use in determining differences between group proportions),
-Regression, single and multiple (and its use in understanding relationships between dependent and independent (explanatory) variables), and
-Optimization modeling (and its use in determining the best solution given a set of constraint).

Various general skills:
-Sampling techniques and issues
-Probability, conditional probability, expected value, and time value of money,
-Probability distributions and descriptive statistics in Excel

I do not know how to solve this question?  Help!!!!!