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#1
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

hey friends i have problem....

the question which asking if patient survive for two year then what is the probability that patient will survive 4 years.....some are saying multiply all four yer probability..some are saying multiply only 3rd and fourth year probability...can anyone explain basic fundamental to give answer of such type of questions...

#2
08-10-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,268 Times in 881 Posts Reputation: 3278

Quote:
 Originally Posted by dr.digant hey friends i have problem.... the question which asking if patient survive for two year then what is the probability that patient will survive 4 years.....some are saying multiply all four yer probability..some are saying multiply only 3rd and fourth year probability...can anyone explain basic fundamental to give answer of such type of questions... THANKS A LOT IN ADVANCE..PLEASE GUYS HELP ME...
First you need the probability of survival. Then this becomes just a conditional probability (given that the patient survived 2 years, what is the probability...).

The probability that event B occurs, given that event A has already occurred is
P(B|A) = P(A and B) / P(A)

 The above post was thanked by: dr.digant (08-10-2011)
#3
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix First you need the probability of survival. Then this becomes just a conditional probability (given that the patient survived 2 years, what is the probability...). The probability that event B occurs, given that event A has already occurred is P(B|A) = P(A and B) / P(A)
hey bebix dint get you....can u explain me in detail????...with example????...are u going to give nbme 4???..bcoz i had question in nbme 4...if u r not giving nbme 4 then i can tell u actual question..so u can explain me better!!!!

#4
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix First you need the probability of survival. Then this becomes just a conditional probability (given that the patient survived 2 years, what is the probability...). The probability that event B occurs, given that event A has already occurred is P(B|A) = P(A and B) / P(A)
u had told that probability of A and B.....P(A and B)...MEANS???...we should add or multiply???..
#5
08-10-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,268 Times in 881 Posts Reputation: 3278

Quote:
 Originally Posted by dr.digant hey bebix dint get you....can u explain me in detail????...with example????...are u going to give nbme 4???..bcoz i had question in nbme 4...if u r not giving nbme 4 then i can tell u actual question..so u can explain me better!!!!
just send me a pm
 The above post was thanked by: dr.digant (08-10-2011)
#6
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix just send me a pm
hey bebix have u got private message???
#7
08-10-2011
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,357 Threads: 194 Thanked 3,268 Times in 881 Posts Reputation: 3278

Quote:
 Originally Posted by dr.digant hey bebix have u got private message???
 The above post was thanked by: dr.digant (08-10-2011)
#8
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix yup...answer is C)
hey bebix i have sent u another private message...if u knw the answer please explain me..thanks a lot!!!

and thanks for nice explaination of previous question too
#9
08-10-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix yup...answer is C)
its also NBME 4 quesstion...
#10
08-11-2011
 USMLE Forums Addict Steps History: Step 1 Only Posts: 127 Threads: 21 Thanked 103 Times in 53 Posts Reputation: 113

Quote:
 Originally Posted by bebix yup...answer is C)
hey bebix please reply the another question which i have sent u in private message...THANKS
#11
01-05-2017
 USMLE Forums Scout Steps History: Step 1 Only Posts: 64 Threads: 16 Thanked 6 Times in 4 Posts Reputation: 16

Quote:
 Originally Posted by dr.digant hey friends i have problem.... the question which asking if patient survive for two year then what is the probability that patient will survive 4 years.....some are saying multiply all four yer probability..some are saying multiply only 3rd and fourth year probability...can anyone explain basic fundamental to give answer of such type of questions... THANKS A LOT IN ADVANCE..PLEASE GUYS HELP ME...
It is conditional probability. Use this formula:P(A|B) = P(B and A) / P(B) and VENN diagram. In this formula P(A andB) is joint area of VENN diagram, in this case 4 year survival is the part of the 2 year survival .Joint area equal the probability of 4 year survival. Probability of 4 year survial= joint area probability(4 year) / 2 year survival

 Tags Biostatistics-Epidemiology

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