Hi All,
I need your help in the calculation of Logit(y)
Logit(y) = -300 + 0.5 * x + 0.3 * y
x=30
value of y is unknown
Thanks
Please recheck your equations. For that value of x, you are asking for the value y such that
logit(y) = -285 + 0.3*y;
Did you really intend to have y on both sides of the equation?
If so...
For the logit function to be defined, y is in (0, 1). The value logit(y) approaches minus infinity as y ->0, so we are looking for a tiny value of y. Therefore we can effectively ignore the term that includes y on the right and approximate the solution by
logit(y) = -285
or
y = logistic(-285) = 1.68E-124.
If y represents the probability of some event, this calculation shows that the probability is effectively 0.
You already have the formula, so where's the problem? In code, you just need this:
data want;
set have; * provides values for y;
x = 30;
result = -300 + 0.5 * x + 0.3 * y;
run;
It seems you are looking for a root of function.
@Rick_SAS wrote some blogs about it .
Please recheck your equations. For that value of x, you are asking for the value y such that
logit(y) = -285 + 0.3*y;
Did you really intend to have y on both sides of the equation?
If so...
For the logit function to be defined, y is in (0, 1). The value logit(y) approaches minus infinity as y ->0, so we are looking for a tiny value of y. Therefore we can effectively ignore the term that includes y on the right and approximate the solution by
logit(y) = -285
or
y = logistic(-285) = 1.68E-124.
If y represents the probability of some event, this calculation shows that the probability is effectively 0.
Thank you - for the explanation.
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