Couldnt you just do the X's together and the Y's and your answer after you divide by each??
Answer:
A) 99.74%
B) 633.6 hours and 986.4 hours
Step-by-step explanation:
Solution :
Given that ,
mean = u =810
standard deviation = sigma = 90
P(540< x <1080 ) = P[(540-810) /90 < (x - u ) / sigma < (1080-810) /90 )]
= P( -3< Z < 3)
= P(Z <3 ) - P(Z < -3)
Using z table
=0.9987-0.0013
= 0.9974
answer=99.74%
(B)
middle 95% of score is
P(-z < Z < z) = 0.95
P(Z < z) - P(Z < -z) = 0.95
2 P(Z < z) - 1 = 0.95
2 P(Z < z) = 1 + 0. 95= 1.95
P(Z < z) = 1.95/ 2 = 0.975
P(Z <1.96 ) = 0.975
z ±1.96
Using z-score formula
x= z * sigma + u
x= -1.96* 90+810
x= 633.6
Using z-score formula
x= z * sigma + u
x=1.96* 90+810
x= 986.4
633.6 hours and 986.4 hours
Answer: 29%
Step-by-step explanation:
