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Old 03-01-2012
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Stats Calculating the relative risk ratio?

the prevalence of breast cancer compared in 2 gp's of women on parity. the following data are obtained at age 70 in both gp's.
children
yes no

yes 120 180 300
breast cancer
no 1380 820 2200

1500 1000 2500

based on these data what is the relative risk(risk ratio) for development of breast cancer in childless women compared to women who have children????

A) 0.67
B) 1.2
C) 1.5
D) 1.8
E) 2.25

ans with explanation plz!!!!!!!!!!!
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Old 03-01-2012
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Please provide the adequate 2x2 box or at least the explain the numbers...
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Quote:
Originally Posted by DocSikorski View Post
Please provide the adequate 2x2 box or at least the explain the numbers...
sorry i was trying to correct it, but couldn't. its from nbme1 block1 Q 26
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E. 2.25

childless women w/e breast cancer = 180 / 1000 = 0.18
women w/ breast cancer + children = 120 / 1500 = 0.08

RR = 0.18 / 0.08
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Quote:
Originally Posted by Dr.NickRiviera View Post
E. 2.25

childless women w/e breast cancer = 180 / 1000 = 0.18
women w/ breast cancer + children = 120 / 1500 = 0.08

RR = 0.18 / 0.08
thanx! your ans is right it's E.
how did you calculate it ??? plz explain me. coz i was doing with first aid formula

a/(a+b)
RR- ------------
c(c+d)
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Quote:
Originally Posted by riya10 View Post
thanx! your ans is right it's E.
how did you calculate it ??? plz explain me. coz i was doing with first aid formula

a/(a+b)
RR- ------------
c(c+d)
don't memorize the quadrants of a table and associate them with a,b,c,d
look at what they are asking

i don't use formulas, i just think it out

but if you want to apply that formula then a would be childless women with breast cancer, and c would be women with children who have breast cancer.
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Quote:
Originally Posted by riya10 View Post
the prevalence of breast cancer compared in 2 gp's of women on parity. the following data are obtained at age 70 in both gp's.
children
yes no

yes 120 180 300
breast cancer
no 1380 820 2200

1500 1000 2500

based on these data what is the relative risk(risk ratio) for development of breast cancer in childless women compared to women who have children????

A) 0.67
B) 1.2
C) 1.5
D) 1.8
E) 2.25

ans with explanation plz!!!!!!!!!!!

looking at the table:
RR would be likelihood in childless women who is positive for breast cancer it is 180 out of the total women who do not have children = 1000
so it would be 180/1000 (for women who dont have kids but have breast cancer)

and then for having kids as well as breast cancer, it would be 120 over the total amount of women who have kids which is 1500
so it would be 120/1500 (for women who have kids and have breast cancer)

and now the RR calculation RR= Child(-)/Disease (+)/child(+)/disease(+)
= (180/1000)/120/1500
=0.18 / 0.08
= 2.25
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Correct Answer thanx

@ Dr. Nick Riviera and
@ usmle taker
thanx alot.
yup! you both are right...
again thanx and good luck!!!
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