12.33 Was the advertising strategy helpful? Among the 100 different varieties of bread made by a bakery, the marketing manager selected the 10 worst-selling bread types and promoted them through a special advertising strategy. Both the mid-month and the end-month sales had an average of 70 packets with a standard deviation of 10 packets considering all the different bread types, and the correlation was 0.50 between the two types of sales. The average for the specially promoted bread types increased from 50 packets in the middle of the month to 60 packets at the end of the month. Can we conclude that the advertising strategy was successful? Explain by identifying the response and explanatory variables and the role of regression toward the mean.