Dnorm isn't the probability - it's the y-value on the density function.  Try
plotting it - it makes a nice normal plot.
See ?dnorm for definition.

Bob


-----Original Message-----
From: Marc Belisle [mailto:marc.m.belisle@usherbrooke.ca] 
Sent: Friday, October 31, 2003 2:40 PM
To: R-Help
Subject: [R] dnorm() lead to a probability >1

Howdee,

One of my student spotted something I can't explain: a probability >1 vs a
normal probability density function.

> dnorm(x=1, mean=1, sd=0.4)
[1] 0.9973557

> dnorm(x=1, mean=1, sd=0.39)
[1] 1.022929

> dnorm(x=1, mean=1, sd=0.3)
[1] 1.329808

> dnorm(x=1, mean=1, sd=0.1)
[1] 3.989423

> dnorm(x=1, mean=1, sd=0.01)
[1] 39.89423

> dnorm(x=1, mean=1, sd=0.001)
[1] 398.9423

Is there a bug with the algorithm?

Thanks,

Marc

========================
Marc Bélisle
Professeur adjoint
Département de biologie
Université de Sherbrooke
2500 boul. de l'Université
Sherbrooke, Québec
J1K 2R1 CANADA

Tél: +1-819-821-8000 poste 1313
Fax: +1-819-821-8049
Courriél: Marc.M.Belisle@USherbrooke.ca
Site Web:
www.usherbrooke.ca/biologie/recherche/ecologie/Belisle/belisle.html

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