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Posted by on Sunday, July 24, 2011 at 3:40pm.

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 < (77-80)/3.5) = P(Z < -3/3.5) = -.857 = .3023

B) P(75.0 < x < 85.0) = P(75-80)/3.5 < Z < (85-80)/3.5) = P(-5/3.5 < Z < 5/3.5) = -1.428 <Z<1.428
.4222+.4222=.8444
C) P(x > 85.0) = .5-

  • stats ( please check) - , Monday, July 25, 2011 at 2:03pm

    A, B. right

    C. Z = 1.428

    Looking it up in the normal distribution table, what is the area in the smaller portion (>85)?

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