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Maths S2 - Poisson Distribution... HELP???

Can anyone explain part (b) to me?

Poisson Distribution Exa3 (Using tables).png

How does...

P(X<b)

become...

P(X \leq b - 1)

Is it because Poisson Cumulative Distribution tables only find probabilities when

P(X \leq x)

so in this example, to find less than b it is the same as thinking of 1 less than equal to b?

(edited 7 years ago)

Reply 1

DylanJ42

[QUOTE="Philip-flop;70225090"]Can anyone explain part (b) to me?

Poisson Distribution Exa3 (Using tables).png

How does...

P(X<b)

become...

P(X \leq b - 1)

Is it because Poisson Cumulative Distribution tables only find probabilities when

P(X \leq x) so in this example, to find [b]less than b[/b] it is the same as thinking of [b]1 less than equal to b[/b]?

poisson only deals with integers. if X is less than an integer then you can say it must be less than or equal to the integer minus 1.

but yes to use tables you have to have less than or equal to

Reply 2

Philip-flop

Original post by DylanJ42

poisson only deals with integers. if X is less than an integer then you can say it must be less than or equal to the integer minus 1.

but yes to use tables you have to have less than or equal to