SOLUTION: The acidity of human blood is measured on a pH scale and is a normal random variable. The mean pH of blood is 7.2 with a standard deviation of 0.15. Find the probability that a ran

Question 1026013: The acidity of human blood is measured on a pH scale and is a normal random variable. The mean pH of blood is 7.2 with a standard deviation of 0.15. Find the probability that a randomly selected person would have a blood pH greater than 7.425. Enter your answer as a decimal number correct to four decimal places.
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
mean = 7.2
standard deviation = .15
threshold score = 7.425

calculate the z-score.

z-score = (threshold score minus mean) / standard deviation.

this becomes z-score = (7.425 - 7.2) / .15.

this results in z-score = .225 / .15 = 1.5.

look up a z-score of 1.5 in the z-score table and it will tell you that the area under the normal distribution curve to the left of a z-score of 1.5 is equal to .9332.

this means that the probability of having a ph score less than 7.425 is .9332.

the probability of having a ph greater than 7.425 is therefore 1 - .9332 = .0668.

that's a 6.68% probability.

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