hzb53jl55v的部落格

標題:

simple probability

發問:

In a university, there are 120 students taking a statistics course. among them, 80 students come from the department of economics, while the rest come from the department of finance. in an exam, 10% of the economics students and 15% of the finance students receive an A grade.Q: An examiner randomly inspects 2... 顯示更多 In a university, there are 120 students taking a statistics course. among them, 80 students come from the department of economics, while the rest come from the department of finance. in an exam, 10% of the economics students and 15% of the finance students receive an A grade. Q: An examiner randomly inspects 2 exam papers with A grade so as to ensure they are properly marked. what are the probabilities of the following events happening? 1. 2 papers belong to students from the same department. (43/91) 2. 2 papers belong to students from different departments. (48/91) please list out the steps needed to get the answers. thanks

最佳解答:

• Homepage被綁架
• 有些檔案需要adobe Reader才可以睇 ，但我開不到它
• 懷孕22週有痔瘡,點算-@1@

• Homepage被綁架
• 有些檔案需要adobe Reader才可以睇 ，但我開不到它
• 懷孕22週有痔瘡,點算-@1@

 

此文章來自奇摩知識+如有不便請留言告知

1. E : a student gets A grade and comes from the department of economics F : a student gets A grade and comes from the department of finance Number of E = 80 x 10% = 8 Number of F = (120 - 80) x 15% = 6 Total number of E and F = 8 + 6 = 14 P(2 students from the same department) = P(EE) + P(FF) = [8C2 / 14C2] + [6C2/14C2] = [(8!/6!2!) / (14!/12!2!)] + [(6!/4!2!) / (14!/12!2!)] = (28/91) + (15/91) = 43/91 2. P(2 students from different departments) = P(EF) = 8C1 x 6C1 / 14C2 = (8!/7!1!) x (6!/5!1!) / (14!/12!2!) = 8 x 6 / 91 = 48/91

其他解答: