题目

英文的统计学问题
An official from the securities commission estimates that 75% of all investment bankers have profited from the use of insider information.If 15 investment bankers are selected at random from the commission’s registry
a).what is the probability that at most 10 but at least 6 have profited from insider information?
b).what is the probability that more than 6 have profited from insider infromation?
c).what is the probability that at most 9 and more than 14 have profited from insider information?
d).what is the expected number of investment bankers who have profited from the use of insider information?

提问时间：2020-08-08

答案

a.
(0.75^6)*(0.25^9)(15C6)+(0.75^7)*(0.25^8)(15C7)+(0.75^8)*(0.25^7)(15C8)+(0.75^9)*(0.25^6)(15C9)+(0.75^10)*(0.25^5)(15C10)=0.3127
b.
1-(0.75^0)*(0.25^15)(15C0)-(0.75^1)*(0.25^14)(15C1)-(0.75^2)*(0.25^13)(15C2)-(0.75^3)*(0.25^12)(15C3)-(0.75^4)*(0.25^11)(15C4)-(0.75^5)*(0.25^10)(15C5)-(0.75^6)*(0.25^9)(15C6)=0.004193
c.
The question does not make any sense.at most 9 and more than 14?
d.
E(x)=np=15*0.75=11.25
You must be taking AP Stats too...well,if you ever need more help,my email is [e-mail].=) Good luck.