SOLUTION: 10. Suppose the random variable X has a normal distribution with mean 9.0 and variance 49. The probability that X takes on a value of at least 18 is approximately equal to A. .0

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Question 1061628: 10. Suppose the random variable X has a normal distribution with mean 9.0 and variance 49. The probability that X takes on a value of at least 18 is approximately equal to
A. .0985
B. .4015
C. .9015
D. Correct approx. answer not given
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Variance of 49 leads to sigma=sqrt%2849%29=7
So then the z score of X=18 is,
z=%2818-9%29%2F7=9%2F7
The probability for this z score is,
P%289%2F7%29=0.900729
So this is the probability that the score is 18 or less.
To find the answer, find the complement.
P=1-0.900729
P=0.099271
D. Correct approx. answer not given