The angiogram is a standard diagnostic test used in clinical medicine to detect

Question

The angiogram is a standard diagnostic test used in clinical medicine to detect strokes in patients. This test has some risks for the patient, and several noninvasive techniques have been developed that are hoped to be as effective as the angiogram. Ore such method utilizes that measurement of cerebral blood flow (CBF) in the brain, since stroke patients tend to have lower levels of CBF than normal. Among healthy people. CBF is normally distributed with mean 75 and standard deviation 17. Patients are classified as being at risk for stroke if their CBF is below 40. Estimate the percentile of patients that have CBF less than 40. Justify your answer. Calculate the z-score for a CBF level of 56. Show your work. Find the exact percentile rank of those with a CBF level beloved 56.

Explanation / Answer

mean =75 sd=17

a. P(x<40) =P(z<(40-75)/17)=P(z<-2.06)=1-P(z<2.06)=1-0.9803=0.0197 (from normal table)

b. z=(56-75)17=-1.12

c. P(x<56)=P(z<-1.12)=1-P(z<1.12)=1-0.8686=0.1314

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