A manufacturer has introduced a new formulation for an existing washing powder, but before launching the product nationally he decides on a regional launch coupled with advertising on television on the local regional station. The manufacturer selects by means of a random sample a number of shops in the region. The sales of the old formulation before the advertisement and the sales of the new formulation after the advertisement were noted. The results were as follows: Shop A B C D E F G H I J Sales before advertisement 79 88 131 103 115 91 57 116 101 94 Sales after advertisement 88 75 141 118 129 88 60 120 109 104 (a) Show, at 5% level of significance, that there is a significant improvement in sales. (12 marks) (b) Do you think that the result of part (a) shows that the new formulation has improved sales? Explain your reasoning.