agriculturalists are interested in determining if there is an increase in corn bushels per acre between one growing season and then the next growing season after being treated with a specialized fertilizer. in year one, 32 plots were randomly selected and their average bushels per acre calculated. in the following year, the same plots were treated with a specialized fertilizer and the average bushels per acre calculated again. the difference between the bushels per acre between both years was compared. what is the true mean difference from one year to the next in terms of average bushels per acre yield after being treated with a specialized fertilizer? what statistical procedure should be used to answer this research question?