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Assume that blood pressure readings are normally distributed with a mean of 115 and a standard deviation of 9.6. if 144 people are randomly? selected, find the probability that their mean blood pressure will be less than 117. round to four decimal places.

Respuesta :

Given:
Mean, μ = 115
Std. dev., σ = 9.6
The sample size of 144 is large enough (> 30) to provide reliable data.

Random variable, x = 117
z-score is
 z = (x - μ)/σ = (117 - 115)/9.6 = 0.2083

From standard tables, obtain
Prob(x < 117) = 0.5825 

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