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has <math>d_1</math>, .6 if he has disease <math>d_2</math>, and .4 if he has disease <math>d_3</math>.  Given that
has <math>d_1</math>, .6 if he has disease <math>d_2</math>, and .4 if he has disease <math>d_3</math>.  Given that
the outcome of the test was positive, what probabilities should the doctor now assign to <math>d_1</math>?
the outcome of the test was positive, what probabilities should the doctor now assign to <math>d_1</math>?
<ul class="mw-excansopts">
<li>4/9</li>
<li>1/2</li>
<li>2/3</li>
<li>3/5</li>
<li>4/5</li>
</ul>


'''References'''
'''References'''


{{cite web |url=https://math.dartmouth.edu/~prob/prob/prob.pdf |title=Grinstead and Snell’s Introduction to Probability |last=Doyle |first=Peter G.|date=2006 |access-date=June 6, 2024}}
{{cite web |url=https://math.dartmouth.edu/~prob/prob/prob.pdf |title=Grinstead and Snell’s Introduction to Probability |last=Doyle |first=Peter G.|date=2006 |access-date=June 6, 2024}}

Latest revision as of 22:50, 22 June 2024

A doctor assumes that a patient has one of three diseases [math]d_1[/math], [math]d_2[/math], or [math]d_3[/math]. Before any test, he assumes an equal probability for each disease. He carries out a test that will be positive with probability .8 if the patient has [math]d_1[/math], .6 if he has disease [math]d_2[/math], and .4 if he has disease [math]d_3[/math]. Given that the outcome of the test was positive, what probabilities should the doctor now assign to [math]d_1[/math]?

  • 4/9
  • 1/2
  • 2/3
  • 3/5
  • 4/5

References

Doyle, Peter G. (2006). "Grinstead and Snell's Introduction to Probability" (PDF). Retrieved June 6, 2024.