A safety light is designed so that the times between flashes are normally distri

Question

A safety light is designed so that the times between flashes are normally distributed with a mean of 3.50 s and a standard deviaiton of 0.40 s. a) Find the probability that an individual time is greater than 4.00 s. b) Fine the probability that the mean for 70 randomly selected times is greater than 4.00 s.

Explanation / Answer

edit undo - Convert the data to z-values ... P(X > 4.50) = P[z > (4.50 - 3.50) / (0.50 / sqrt 50)] = P(z > 14.1) Looking up P(z > 14.1) in a Standard Normal table, you will find that the largest z-value is about 3.5, so ... P(z > 14.1) = 0 Hope that helps

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