# SOLUTION: X has a normal distribution with a mean of 75.0 and a standard deviation of 2.5. Find the following probabilities: a) P(x < 70.0) i did 70-75/2.5= -2 but dont know what's next

Algebra ->  Algebra  -> Probability-and-statistics -> SOLUTION: X has a normal distribution with a mean of 75.0 and a standard deviation of 2.5. Find the following probabilities: a) P(x < 70.0) i did 70-75/2.5= -2 but dont know what's next       Log On

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 Click here to see ALL problems on Probability-and-statistics Question 186305: X has a normal distribution with a mean of 75.0 and a standard deviation of 2.5. Find the following probabilities: a) P(x < 70.0) i did 70-75/2.5= -2 but dont know what's next b) P(72.5 < x < 80.0) not sure c) P(x >82.5) 75-82.5/2.5= -3 i use table to look for z 3=0.3821 p(z<-3)=0.3821 Answer by stanbon(57282)   (Show Source): You can put this solution on YOUR website!X has a normal distribution with a mean of 75.0 and a standard deviation of 2.5. Find the following probabilities: ----------------------- a) P(x < 70.0) i did (70-75)/2.5= -2 but dont know what's next P(x < 70) = P(z < -2) = 0.0228 --------------------------------------- b) P(72.5 < x < 80.0) not sure z(72.5) = (72.5-75)/2.5 = -2.5/2.5 = -1 z(80) = (80-75)/2.5 = 2 P(72.5 < x < 80) = P(-1 < z < 2) = 0.8186 ---------------------------------------------------- c) P(x >82.5) z(82.5) = (82.5-75)/2.5 = 3 P(x > 82.5) = P(z > 3) = 0.0013 ========================================== Cheers, Stan H.