DEL R. answered • 10/25/19

Expert Math and Stats Tutor

a) What percent of Parkway High School history students earn an A?

A= Student had Dr.Mima

B= Student had Dr.P

C= Student earned "A"

P(A)= 0.40 P(B)=0.60 P(C|A)= 0.30 P(C|B)=0.10

P(C)=P(A)P(C|A) + P(B)P(C|B)

= (0.40)(0.30) + (0.60)(0.10)

**P(C) = 0.18 **

b) Tiffany did not earn an A in english. What is the probability that Tiffany had Dr.P for history?

-- if the question was about Dr. P teaching __English__:

C' = complement of event C = student not earning "A"

P(B| C') = P(C'|B)P(B) / P(C')

P(C')= 1-P(C) = 1-0.18= 0.82

P(C'|B)= 1-P(C|B) = 1-0.10=0.9

P(B| C') = 0.9*0.6 / 0.82 = calculate!

2a - use binomial. 2c-.Use negative binomial. 2d- use negative binomial but calculate the p using binomial.

Good luck!