Whole Blood can now be stored up to 42 days before use. The relative risk of pos

Question

Whole Blood can now be stored up to 42 days before use. The relative risk of postoperative death increased by 30% in patients given blood that had been stored more than two weeks. Suppose the age of the stored blood units is normally distributed with a mean of 20 days and a standard deviation of 8 days. Find the Following:

A) Percentage of units that are considered outdated at 42 days.

B) Percentage of units considered outdated using the 2-week standard.

C) Probability of not receiving outdated blood if you were given three units under the new 2 week standard.

Explanation / Answer

A) From informatio given, Xi=42, Xbar=20, s=8. Substitute the values in following eqaution to obtain the z score.

z=(Xi-Xbar)/s=(42-20)/8=2.75

P(X>42)=P(z>2.75)=0.0030~0.3%

B) Xi=14, Xbar=20, s=8

z=(14-20)/8=-0.75

P(X>20)=P(z>-0.75)=0.7734~77.34%

C) P(outdated bloodC)=1-(0.7734)^3=0.5374.

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