Statistical Inference A retailer believes that its new advertising strategy will increase sales. Previously, the mean spending in 15 categories of consumer items in both the 18-34 and 35+ age groups was $70.00. (For all hypothesis tests, assume the level of significance is 0.05). Formulate a hypothesis test to determine if the mean spending in these categories has statistically increased. b. After the new advertising campaign was launched, a marketing study found that the mean spending for 300 respondents in the 18-34 age group was $75.86, with a standard deviation of $50.90. Is there sufficient evidence to conclude that the advertising strategy significantly increased sales in this age group? c. For 700 respondents in the 35+ age group, the mean and standard deviation were $68.53 and $45.29 respectively. Is there sufficient evidence to conclude that the advertising strategy significantly increased sales in this age group? a