2. Peter is a door-to-door sales representative who makes a sale at only 8% of his house calls. If Peter makes 219 house calls today, what is the probability that:
(a) he makes a sale at 12 or fewer houses?
Someone was trying to help me and said 12 x 100/219 = 5.6% but I have no idea where the 100/219 comes into play.
(b) he makes a sale at 20 or fewer houses?
(c) he makes a sale at 15 to 25 houses?
For part C
You have to calculate
P(X = 15) + P(X = 16) + P(X = 17) + P(X = 18) + P(X = 19) + P(X = 20) + P(X = 21) + P(X = 22) + P(X = 23) + P(X = 24) + P(X = 25)
X ~ Binomial(n = 219, p = 0.08)
to find P(x=15) = ( 219 C 15 )(0.08)^15(1-0.08)^204
Now you have to calculate the rest and add them together.