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Q: 23 Testing for a disease can be made more efficient by combining samples. If

ID: 3294081 • Letter: Q

Question

Q: 23

Testing for a disease can be made more efficient by combining samples. If the samples from six people are combined and the mixture tests negative, then all six samples are negative. On the other hand, one positive sample will always test positive, no matter how many negative samples it is mixed with. Assuming the probability of a single sample testing positive is 0.2, find the probability of a positive result for six samples combined into one mixture. Is the probability low enough so that further testing of the individual samples is rarely necessary? The probability of a positive test result is Is the probability low enough so that further testing of the individual samples is rarely necessary? A. The probability is not low, so further testing of the individual samples will not be a rarely necessary event B. The probability is not low, so further testing will be necessary for all of the combined mixtures C. The probability is not low, so further testing will not be necessary for any of the mixtures D. The probability is not low, so further testing of the individual samples will be a rarely necessary event.

Explanation / Answer

p = 0.2

q = 1 - p = 0.8

n= 6

To find P(X = at least 1 ) = 1 - P(X =0)

P(X=0) = 0.86 = 0.2614

So, answer to first question:

0.2614

Answer to second question:

Correct option

A. The probability is not low, so further testing of the individual samples will not be a rarely necessary event.