105. The Director of Emergency Medicine at Big Mountain MedicalServices is study

Question

105. The Director of Emergency Medicine at Big Mountain MedicalServices is studying patient waiting time. Waiting time is definedas the time from when a patient enters the facility until seen by aphysician. The study indicates the waiting time follows a normaldistribution with a mean of 22

minutes and a standard deviation of 8 minutes.

a. What fraction of the patients is seen in between 15 and 22minutes?

b. What fraction is seen in less than 15 minutes?

c. What fraction is seen in more than 15 minutes but less than32 minutes?

d. What fraction is seen in more than 25 minutes but less than32 minutes?

e. Five percent of the patients are seen in how many minutes orless? That is, how quickly are 5

percent of the patients seen?

Explanation / Answer

So all we need to do is look at a Z table. If the mean is 22, and the standard deviation is 8. A. From 15 - 22 is just 1 sd below to the mean ~34.5% B. Under 15 is all scores under 1 standard deviation ~15.5% (Percent of scores under Z of -1). For the rest, use the formula z = (score (score you're lookingat) - mean) / standard deviation. Then look it up on a z table. For the ones that are between. Do the higher number, getthe z score and corresponding number, then subtract the lowernumber from the lower z score.

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