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testing for a disease can be made more efficient by combining samples. If the samples from two people are combined and the mixture tests​ negative, then both 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 0.15​, find the probability of a positive result for two samples combined into one mixture. Is the probability low enough so that further testing of the individual samples is rarely​ necessary?w./search?q=%E2%80%8B"At+least%E2%80%8B+one"+is+equivalent+to%E2%80%8B+_______.&oq=%E2%80%8B"At+least%E2%80%8B+one"+is+equivalent+to%E2%80%8B+_______.&aqs=chrome..69i57j0i22i30l3.409j0j4&sourceid=chrome&ie=UTF-8 The probability of a positive test result is nothing

Sagot :

Answer:

(a) [tex]P(Two\ Positive) = 0.2775[/tex]

(b) It is not too low

Step-by-step explanation:

Given

[tex]P(Single\ Positive) = 0.15[/tex]

[tex]n = 2[/tex]

Solving (a):

[tex]P(Two\ Positive)[/tex]

First, calculate the probability of single negative

[tex]P(Single\ Negative) =1 - P(Single\ Positive)[/tex] --- complement rule

[tex]P(Single\ Negative) =1 - 0.15[/tex]

[tex]P(Single\ Negative) =0.85[/tex]

The probability that two combined tests are negative is:

[tex]P(Two\ Negative) = P(Single\ Negative) *P(Single\ Negative)[/tex]

[tex]P(Two\ Negative) = 0.85 * 0.85[/tex]

[tex]P(Two\ Negative) = 0.7225[/tex]

Using the complement rule, we have:

[tex]P(Two\ Positive) = 1 - P(Two\ Negative)[/tex]

So, we have:

[tex]P(Two\ Positive) = 1 - 0.7225[/tex]

[tex]P(Two\ Positive) = 0.2775[/tex]

Solving (b): Is (a) low enough?

Generally, when a probability is less than or  equal to 0.05; such probabilities are extremely not likely to occur

By comparison:

[tex]0.2775 > 0.05[/tex]

Hence, it is not too low