**Marginally significant » Rstats**, and kindly contributed to R-bloggers)

Today is my birthday. It’s also the birthday of a close friend. What an incredible coincidence! Or wait, may be is just expected. One more time R comes into our help, because it has a built-in function to answer our question.

Which is the probability of two coincident anniversaries among a group of 17 people? (yes we have a mailing list, so I can count my friends semi-objectively without the fear of not counting them all). Just type:

`pbirthday(n= 17, classes = 365, coincident = 2)`

The answer is approximately 0.3, that is 3 of every 10 friend groups (of that size) have at least two anniversaries that coincide. Not that impressive, isn’t it?. But the beauty of stats is that **stats are here to correct your intuition.** To have an impressive coincidence (and statistical significant) you will need a group of 47 people, none of them with coinciding birthdays. And then, probably nobody will be amazed.

`qbirthday(prob = 0.95, classes = 365, coincident = 2)`

Anyway, happy birthday to all readers celebrating today (if any)!

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**Marginally significant » Rstats**.

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