stats ( please check)
posted by Celest on .
6. X has a normal distribution with a mean of 80.0 and a standard deviation of 3.5. Find the following probabilities:
(A) P(x < 77.0)
(B) P(75.0 < x < 85.0)
(C) P(x > 85.0) (Points : 6)
I think I have the first two but I am stumped on the third one. Thank you for your help!!
A) P(x < 77.0) = P(Z < (7780)/3.5) = P(Z < 3/3.5) = .857 = .3023
B) P(75.0 < x < 85.0) = P(7580)/3.5 < Z < (8580)/3.5) = P(5/3.5 < Z < 5/3.5) = 1.428 <Z<1.428
.4222+.4222=.8444
C) P(x > 85.0) = .5

A, B. right
C. Z = 1.428
Looking it up in the normal distribution table, what is the area in the smaller portion (>85)?