Probability,pls help to check solution D

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malcolmmalcolmm

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There is a pandemic in Absurdistan. At any time there is a 70% chance
that someone has the disease. Luckily there is a test for infection, but of
the tests performed, 10% gave a false positive result and 5% of them gave
a false negative. If you got a positive result from the test, what is the
probability that you are really infected? If you tested negative, what is the
probability that you are not infected?


So the solution
Imagine a population of 1000. 70%, 700, have the disease, 300 do not. Of the 700 who have the disease, 5%, 35, test negative, the other 665 test positive. Of the 300 who do not have the disease, 10%, 30, test positive, the other 270 test negative.

So a total of 665+ 30= 695 test positive of whom 665 actually have the disease.

Could you please help?
 
malcolmmalcolmm said:
There is a pandemic in Absurdistan. At any time there is a 70% chance
that someone has the disease. Luckily there is a test for infection, but of
the tests performed, 10% gave a false positive result and 5% of them gave
a false negative. If you got a positive result from the test, what is the
probability that you are really infected? If you tested negative, what is the
probability that you are not infected?


So the solution
Imagine a population of 1000. 70%, 700, have the disease, 300 do not. Of the 700 who have the disease, 5%, 35, test negative, the other 665 test positive. Of the 300 who do not have the disease, 10%, 30, test positive, the other 270 test negative.

So a total of 665+ 30= 695 test positive of whom 665 actually have the disease.

Could you please help?
Click to expand...
This solution was provided to you at:

Probability questions explanation needed

1)There are 2 yellow balls in a box. How many red balls need to be added if we want exactly 21 different orders of drawing all the balls? 2) Suppose a kangoroo lives on the real line and can perform unit length jumps in either the positive or negative direction. How many different ways can he...
www.freemathhelp.com

Where is your work/understanding? There is about one line of work is needed to answer the question/s posed in your original post. Please show some of your work.
 
So as far as I understood, 665+ 30= 695 test positive of whom 665 actually have the disease.
and 270+35=305 test negative
But I am not able to finish it, they are asking for the probability.
I am studying in a different faculty so I am asking for help for my friend and here I really want to thank you, but could you please help to finish it?
Thanks
 
malcolmmalcolmm said:
So as far as I understood, 665+ 30= 695 test positive of whom 665 actually have the disease.
and 270+35=305 test negative
But I am not able to finish it, they are asking for the probability.
I am studying in a different faculty so I am asking for help for my friend and here I really want to thank you, but could you please help to finish it?
Thanks
Click to expand...
Since you cannot start the problem - we will begin with relevant definitions

Please give us the definition of PROBABILITY from your (or your friend's) textbook or class-notes.
 
it is about the happening random event. For example, when a coin is tossed in the air, the possible outcomes are Head and Tail.
favorable event/all event
 
usersureuser44 said:
it is about the happening random event. For example, when a coin is tossed in the air, the possible outcomes are Head and Tail. favorable event/all event
Click to expand...
Correct! Now let's do a simple problem:
Suppose you have a well-shuffled deck of playing cards - with 4 suits and 13 cards in each suit - total 52 cards.

What is the probability of drawing a club from the deck of cards?
 
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