Stats Numbers need to treat (NNT) help

[OrthoRehab33]

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I have conflicting sources or more likely I'm not understanding the reasoning, hopefully someone can help!

The question is comparing a new drug "X" with control medication to see if drug X is more effective at reducing cancer.

So our 2x2 looks like this: Cancer+ drug X= 10pts Cancer+ Control= 25 (So boxes A and B are 10 and 25 respectively) No cancer+ drug X= 990pts No cancer+ control= 975pts (C and D respectively)

Now in first aid the equation for ARR is c/c+d - a/a+b
But they solved the equation by subtracting the event rate in the tx group (10/1000) - from the event rate in control group (25/1000). Thus doing 0.025-0.01= o.o15%
So essentially they did b/b+d - a/a+c
So, Im just confused how they got the absolute risk reduction equation.

 

[DandyLion]

Your 2x2 should have the disease (cancer) along the top with the intervention (drug X) along the side.

Therefore,
A = Cancer + Drug X = 10
B = No Cancer + Drug X = 990
C = Cancer + Control = 25
D = No Cancer + Control = 975

ARR = (c/c+d) - (a/a+b)
ARR = (25/25+975) - (10/10+990)
ARR = 0.025 - 0.01
ARR = 0.015

 

[OrthoRehab33]

Your 2x2 should have the disease (cancer) along the top with the intervention (drug X) along the side.

Therefore,
A = Cancer + Drug X = 10
B = No Cancer + Drug X = 990
C = Cancer + Control = 25
D = No Cancer + Control = 975

ARR = (c/c+d) - (a/a+b)
ARR = (25/25+975) - (10/10+990)
ARR = 0.025 - 0.01
ARR = 0.015

Thank you!