normal distribution

Question

the mean clotting time of blood is 7.45 seconds with a standard deviation of 3.6 seconds. what is the probability that an individual's clotting time will be less than 4 seconds or greater than 9 seconds? assume a normal distribution. this problem can't be solved using technology or the table for the standard normal curve from your text.

the probability is _.

(round to 4 decimal places as needed.)

Answer 1

z = (x - μ)/σ = (x - 7.45)/3.6; x = 3.6z + 7.45;

Now x < 4 or x > 9

3.6z + 7.45 < 4 or 3.6z + 7.45 > 9

z < - 0.9583 or z > 0.4306

P(z < - 0.9583 or z > 0.4306) = 0.1627 + 0.3315 = 0.4942