题目

已知回归方程为=0.50x-0.81,则x=28时，y的估计值为___________. 答案：解析：y的估计值为0.50×28-0.81=13.19.答案：13.19---I haven’t got the reference book yet, but I’ll have a test on the subject next month.---Don’t worry. You _______ have it by Friday.A. could B. shall C. must D. may