# Sexy Stats 1 QuestionWatch

This discussion is closed.
#1
Hello here tis:

A contractor bids for two buildings. He estimates that the probability of winning the first project is 0.5, the probability of winning the second is 0.3 and the probability of winning both projects is 0.2.

(a) Find that probability that he does not win either project.

(b) Find the probability that he wins exactly one project.

(c) Given that he does not win the first project, find the probability that he wins the second.

(d) By calculation, determine whether or not winning the first contract and winning the second contract are independent events.

THANKS xoxox
0
13 years ago
#2
(Original post by ClaireC)
Hello here tis:

A contractor bids for two buildings. He estimates that the probability of winning the first project is 0.5, the probability of winning the second is 0.3 and the probability of winning both projects is 0.2.

(a) Find that probability that he does not win either project.

(b) Find the probability that he wins exactly one project.

(c) Given that he does not win the first project, find the probability that he wins the second.

(d) By calculation, determine whether or not winning the first contract and winning the second contract are independent events.

THANKS xoxox

This might be right:
(a) 0.35
(b) 0.45

(d) are independent
0
#3
its not

i did that too, but the answers are

a. 0.4
b. 0.4
c. a fifth
0
13 years ago
#4
a) P(A'UB') = P(A')+ P(B') - P(A'nB')
0.5+0.7 - 0.8 = 0.4
0
13 years ago
#5
P(1) =0.5
P(2) = 0.3
P(1 n 2) = 0.2

a)
so P(1 only) = 0.5 - 0.2 = 0.3 (see attachment)
P(2 only) = 0.3-0.2 = 0.1
so P(neither) = 1 - (0.3+0.2+0.1)
P (neither) = 0.4

b)
P(exactly 1) = (1 and none) or P(2 and none)
P = 0.3 + 0.1
P = 0.4

c)
using P(A / B) = P(A and B)/P(B)
P(2 / 1' ) = P(2 and 1')/P(1')
P(2 / 1' ) = 0.1/(0.1+0.4)
= 0.2

d) independent because P(1 / 2) = P(1)
0
#6
P(2 / 1' ) = P(2 and 1')/P(1')
P(2 / 1' ) = 0.1/(0.1+0.4)
how'd you go between those lines?
0
#7
HELP SOMEONE

part c)
0
13 years ago
#8
Look at his Venn diagram.
P(2 and 1') = 0.1
P(1') = 0.1 + 0.4 (the bit inside the 2 only, plus the remaining 0.4 outside)
0
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