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I am trying to calculate P(x>=3) using R. What I wrote is the following;
ppois(3,4.5) #this returns 0.342296
the problem here is that the value is for (Px<=3). I know that including "lower = FALSE" will return P(X>3)
ppois(3,4.5,lower=FALSE) #This returns 0.657704 which is P(X>3)
What would I have to modify or include to return P(X>=3)?
Note that $ P(X \ge 3)$ is equivalent to $P(X > 2)$
We can then calculate the following probability as follow: \begin{equation} P(X > 2) = 1-P(X \le 2) = 0.8264 \end{equation}
We can then compute the desired probability using R:
# P(X>2) ppois(2,4.5, FALSE) #OR # 1-P(X<=2) 1-ppois(2,4.5)
Output:
0.8264219
As a side note - RStudio is a R Integrated Development Environment (IDE)
lower.tail=FALSE
ppois
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