Suppose we diagnose people as being healthy if their serum uric acid level is less than 6.75mg/100ml and as having gout if the level is more than 6.75mg/100ml.
(i) What is the probability of a person with gout being correctly diagnosed? (5 marks)
(ii) What is the probability that a healthy person will be diagnosed as having gout? (5 marks)
(iii) If 30 healthy people take the test in a given week, what is the probability that exactly three people will be diagnosed as having gout in that week?(5 marks)
Julius N
(i)
for people with gout, P(X>6.75) is probability of being diagnosed with gout:
z= ( x - µ ) / σ:
x= 6.75-->z= -1.75;
P(X>6.75 )= P(z> -1.75)=0.959941 = 96%
(ii)
for normal people
z= ( x - µ ) / σ: x= 6.75-->z= 1.75;
P(X>6.75 )= P(z> 1.75)=0.040059 = 4%
(iii) using the binomial distribution here are some of the various probabilities:
Binomial Distribution: n= 30 p= .040059 µ = 1.20177 ; σ = 1.074071
-- X -- P(X) -------- Σ P(X)
0: 0.293316323, 0.293316323,
1: 0.367208777, 0.660525100,
2: 0.222196196, 0.882721297,
3: 0.086542405, 0.969263702,
4: 0.024377451, 0.993641154,
5: 0.005289897, 0.998931050,
so the P(exactly three normal people getting diagnosed as having gout) = 0.086542405 = 9%
Orignal From: (a) A standard test for gout is based on the serum uric acid level. probabilitys?
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