A nationally known supermarket decided to promote its own brand of soft drinks on TV for two weeks. Before the ad campaign, the company randomly selected 40 of its stores across the United States to be part of a study to measure the campaign’s effectiveness. During a specified half-hour period on a certain Monday morning, all the stores in the sample counted the number of cans of its own brand of soft drink sold. After the campaign, a similar count was made. The average difference was an increase of 70 cans, with a standard deviation of difference of 10 cans. Does this data support effectiveness of the ad on TV? Answer the question applying the appropriate statistical method, and interpret the result you obtained.