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.