A university found that 20% of its students withdraw without completing the intr

Question

A university found that 20% of its students withdraw without completing the introductory statistics course. Assume that 20 students registered for the course.

Compute the probability that 2 or fewer will withdraw.

Compute the probability that exactly 4 will withdraw.

Compute the probability that more than 3 will withdraw.

Compute the expected number of withdrawals.

Please help me with these questions

In the text problem you considered a course with 20 students enrolled. Consider a course with 8 students enrolled. For a course with 8 students enrolled use the box below to enter the probability mass function using a histogram and table approach

p.m.f table

Histogram

Explanation / Answer

a) P = 0,1,2 withdrew = 0.8^20+20*0.2*0.8^19+190*0.2^2*0.8^18=0.2060

b) P( 4) = 20C4 * 0.2^4*0.8^16=20!/[16!*4!]* 0.2^4*0.8^16=0.218199

b) P( more than 3) = 1-P( 0,1,2,3) = 1-[ 0.8^20+20*0.2*0.8^19+190*0.2^2*0.8^18+1140*0.8^17*0.2^3]=0.5885

d) Expected withdrawals=np=20*0.2=4

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