a blood testing procedure is made more efficent by combining samples of blood specimens. if samples from 5 diff people are combined and the mixture tests negative, we know that all 5 individual samples are negative. find the probability of a positive result for 5 samples combines into one mixture, assuming the probability of a individual blood sample testing positive is 0.015
2006-11-30 17:50:26 · 2 answers · asked by socom_lover 2 in Science & Mathematics ➔ Mathematics
You want the prob that at least one of the five is positive.
"at least one" problems are nearly always best done by finding
prob(none) and then subtracting from 1.
What's the prob that a blood sample tests negative? 1 - 0.015
Raise this to the fifth power to find prob that all five test negative.
Subtract from 1 to get prob of at least one positive.
2006-11-30 17:55:13 · answer #1 · answered by Hy 7 · 1⤊ 0⤋
Wouldn't this be like a binomial model where you're taking a sample of 5, where p=0.015 ?
So, a positive result for the mix means at least one of the 5 is positive. At least one is 1-P(none of the 5)
None of the 5 is:
5C0*p^0*(1-p)^5 is what you need to calculate.
5C0 is 5 chose 0 which equals 1.
You do the rest while I find my calculator.
Btw, the guy about me is correct. It's just a less general solution.
2006-12-01 01:56:19 · answer #2 · answered by modulo_function 7 · 0⤊ 0⤋