A study was conducted assessing the effect of observer training on measurement o

ID: 3329306 • Letter: A

Question

A study was conducted assessing the effect of observer

training on measurement of blood pressure based on

NHANES data from 1999–2000 (Ostchega, et al., [1]). A

goal was that the difference in recorded blood pressure

between the observer and trainer be 2 mm Hg in absolute

value. It was reported that the mean difference in systolic

blood pressure (SBP) between observers and trainers (i.e.,

mean observer SBP minus trainer SBP) = mean () was

0.189 mm Hg with sd = 2.428 mm Hg.

5.11 If we assume that the distribution of is normally distributed,

then what is the 90 percentile (i.e., the upper decile)

and 10 percentile (i.e., the lower decile) of the distribution?

Ans:

mean=0.189

standard deviation,sd=2.428

90th percentile means that

P(X<=x)=0.9

z=1.282

x=0.189+1.282*2.428=0.189+3.113=3.302

90th percentile is 3.302

10th percentile means that

P(X<=x)=0.1

x=0.189-1.282*2.428=0.189-3.113=2.924

10th percentile is 2.924

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