[R] Question regarding dnorm()
S Ellison
S.Ellison at LGCGroup.com
Wed Sep 14 13:37:47 CEST 2011
You have calculated density, not probability.
Probability is in [0,1]; density is in [0,Inf)
And for a continuous variable, density cannot be interpreted as a probability or a frequency.
S
> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of Vincy Pyne
> Sent: 14 September 2011 12:24
> To: r-help at r-project.org
> Subject: [R] Question regarding dnorm()
>
> Hi,
>
> I have one basic doubt. Suppose X ~ N(50,10).
>
> I need to calculate Probability X = 50.
>
> dnorm(50, 50, 10) gives me
> [1] 0.03989423
>
> My understanding is (which is bit statistical or may be
> mathematical) on a continuous scale, Probability of the type
> P(X = .....) are nothing but 1/Infinity i.e. = 0. So as per
> my understanding P(X = 50) should be 0, but even excel also
> gives 0.03989422. Obviously my understanding is wrong. If I
> put value of x = 0 in the normal density function, I do get
> 0.03989422.
>
> My confusion is on the continuous scale if the probability (X
> = x) doesn't make sense, 0.03989423 is significant to neglect.
>
> Please clarify
>
> Regards
>
> Vincy
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> *******************************************************************
This email and any attachments are confidential. Any use...{{dropped:8}}
More information about the R-help
mailing list