q.11_________? - sarim

[ArchivalUser]

The prevalence of breast cancer is compared in two groups of women based on parity.The following data are obtained at age 70 in both groups



................(Women Had Children)..........(Childless Women)

No Breast ca...... 920 ....................................820..............(1740)
Breast cancer..... 80 .....................................180...............(260)

......................(1000)..................................(1000)............(2000)

Based on these data what is the Relative risk(Risk Ratio) for development of Breast cancer in childless women compared with women who have children?

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

[ArchivalUser]

E,ty

[ArchivalUser]

E
i'm new to biostats.
so the formula for relative risk is Incidence of exposed / Incidence of unexposed.
and Incidence is calculated by a.) 180/180+820 = 0.18
b.) 80/1000 = 0.08

relative risk = 0.18/0.08 = 2.25

[ArchivalUser]

nice

[ArchivalUser]

@sarim

Thank you for all the questions. I wonder if the above calculation is true for "prevalence" as well, because i remember in risk ratio calculation we need "incidence" rate in two groups.

[ArchivalUser]

Thanks for the Qs sarim. I am bookmarking all your qs . Will solve them after I do biostat. I appreciate your help buddy

[ArchivalUser]

@Shool..... I think not ( if i'm understanding ur Q correctly) and u r very welcome.

@medicus ... most welcome

[ArchivalUser]

@sarim

I mean in the stem prevalence has been given but for calculating RR we need incidence.

[ArchivalUser]

I see.

Here we are going to treat this prevalence data as an Incidence rate. Why ? look at the last line of the Q:

"Based on these data what is the Relative risk(Risk Ratio) for DEVELOPMENT of Breast cancer in childless women compared with women who have children?"


The study itself is like a "RETROspective Cohort", where every thing already has happened (Exposure and the Outcome)

-where back in time we determined the "Exposure Status" (Being Childless vs Had Children) and tracked them down for the development of Breast cancer

-We obtained the data at the age of 70 yrs; but those who got the cancer must have had the Cancer incidence at different ages, which is now gathered as prevalence data.


I don't know if that makes any sense.

[ArchivalUser]

you are right, makes perfect sense. Thank you so much.