Mouthful of Risks and Ratios

Assalamualaikum. In the Name of Allah the Most Beneficent the Most Merciful.


This block we learnt a lot about all kinds of risks and ratios. I get confused. So I'd like to share the following with those who are as confused as I am. They're just explanations that makes you understand. Don't quote me in the exams... :P (definitions are from Wiki, so... hehehehe...)


Relative risk and attributable risk


Relative risk (RR):
Relative risk (RR) is the risk of an event (or of developing a disease) relative to exposure. Relative risk is a ratio of the probability of the event occurring in the exposed group versus a non-exposed group.
It's like, group A smoke and group B don't smoke. In the end, group A with lung cancer vs group B with lung cancer, the ratio is measured. Of course la group A is more right? So if the RR is greater than 1.0, it indicates a positive association. If RR is smaller than 1.0, it indicates a protective effect.


Attributable risk: 
Attributable risk is the difference in rate of a condition between an exposed population and an unexposed population.
It's like, [the incidence of lung CA in group A] - [the incidence of lung CA in group B]. Note that this time it's minus (tolak, whatever you call it in BM), not RATIO wor...


Absolute and Relative Risk


Absolute risk:
It's like, hmmm, just plain risk. Like, if you eat Nasi Lemak, the risk of you falling asleep in class is 90%. Something like that. Just plain risk, not much comparison.


Odds ratio:
This is a bit odd. You see the equation is like "ad/bc" WTH? It is the ratio of the ratio of two outcomes. WTH again. Simple actually.
First you have that D+ D- and E+ E- table right? (the 2 by 2 or conventional table). First you have the diseased group, both exposed and not exposed. OK, find the ratio between Exposed : Not Exposed, under this Disease group. Then you have the no-disease group, find the ratio of Exposed : Not Exposed again. Now you have two ratios, one for each outcome right? OK, then, you find the ratio between these two outcomes.
To make it simple (if you still can't understand...), use the table in our notes that has the letters a b c d:
First ratio I told you to find [ a : c ]
Then I told you to find [ b : d ]
Then, for Odds Ratio, you're supposed to find [ a : c ] : [ b : d ]
I know it looks different from the original formula, ad/bc; so [ a : c ] : [ b : d ] can be simplified into:
[a : c] : [b : d]
= ( a / c ) / ( b / d )
= ( a / c ) x ( d / b )
= ( a d ) / ( c b )          [it's from the notes laa...]


I'll add more if I found any.