A new small business wants to know if its current radio advertising is effective. The owners decide to look at the mean number of customers who make a purchase in the store on days immediately following days when the radio ads are played as compared to the mean for those days following days when no radio advertisements are played. They found that for 15 days following no advertisements, the mean was 17.4 purchasing customers with a standard deviation of 1.5 customers. On 13 days following advertising, the mean was 17.9 purchasing customers with a standard deviation of 1.1 customers. Test the claim, at the 0.05 level, that the mean number of customers who make a purchase in the store is lower for days following no advertising compared to days following advertising. Assume that both populations are approximately normal and that the population variances are equal. Let days following no advertisements be Population 1 and let days following advertising be Population 2. Required:
a. Compute the value of the test statistic.
b. Do we fail to reject OR reject the null hypothesis because of sufficient or insufficient evidence?