Question

g Bonus: Assume that among the general pediatric population, 7 children out of every 1000 have DIPG (Diffuse Intrinsic Pontine Glioma, an aggressive brain cancer). A pharmaceutical company designs a screening test for DIPG that has a 98% sensitivity and an 84% specificity. Given that someone has a positive test result, what is the probability they don't have DIPG

Answer 1

Answer:

0.9586

Step-by-step explanation:

From the information given:

7 children out of every 1000 children suffer from DIPG

A screening test designed contains 98% sensitivity & 84% specificity.

Now, from above:

The probability that the children have DIPG is:

$\mathbf{P(positive) = P(positive \ | \ DIPG) \times P(DIPG) + P(positive \ | \ not \DIPG)\times P(not \ DIPG)}$$= 0.98\imes( \dfrac{7}{1000}) + (1-0.84) \times (1 - \dfrac{7}{1000})$

= (0.98 × 0.007) + 0.16( 1 - 0.007)

= 0.16574

So, the probability of not having DIPG now is:

$P(not \ DIPG \ | \ positive) = \dfrac{ P(positive \ | \ not DIPG)\timesP(not \ DIPG)} { P(positive)}$

$=\dfrac{ (1-0.84)\times (1 - \dfrac{7}{1000}) }{ 0.16574}$

$=\dfrac{ 0.16 ( 1 - 0.007) }{0.16574}$

= 0.9586