<PRE><B>Question 41639</B>
For 2000 patients, blood-clotting time was normally distributed with a mean of 8 seconds and a standard deviation of 3 seconds. What percent had blood-clotting times between 5 and 11 seconds?
MEAN=8
S.D=3
N=2000
S.E.=S.D/SQRT(N)=3/SQRT(2000)=0.06708
VARIATION FROM MEAN =8-3=5 AND 8+3=11
WE FIND 3=0.06708*K
K=44.7
THAT IS WE WANT % LIMITS FOR 44.7SIGMA...IT IS ALMOST 100%
SO ALMOST 100% OF PATIENTS WILL HAVE CLOTTING TIME OF 5 TO 11 SECS. </PRE>