how to generate a normal distribution with mean=1, min=0.2, max=0.8

Surely you must be joking, Mr. Jianfeng.

On Apr 28, 2011, at 12:09 PM, Ravi Varadhan wrote:

Surely you must be joking, Mr. Jianfeng.

Perhaps not joking and perhaps not with correct statistical  
specification.

A truncated Normal could be simulated with:

set.seed(567)
x <- rnorm(n=50000, m=1, sd=1)
xtrunc <- x[x>=0.2 & x <=0.8]
require(logspline)
plot(logspline(xtrunc, lbound=0.2, ubound=0.8, nknots=7))

-- 
David.

-------------------------------------------------------
Ravi Varadhan, Ph.D.
Assistant Professor,
Division of Geriatric Medicine and Gerontology School of Medicine  
Johns Hopkins University

Ph. (410) 502-2619
email: rvaradhan at jhmi.edu


-----Original Message-----
From:

r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org 

] On Behalf Of Mao Jianfeng
Sent: Thursday, April 28, 2011 12:02 PM
To: r-help at r-project.org
Subject: [R] how to generate a normal distribution with mean=1,  
min=0.2, max=0.8

Dear all,

This is a simple probability problem. I want to know, How to  
generate a
normal distribution with mean=1, min=0.2 and max=0.8?

I know how the generate a normal distribution of mean = 1 and sd =

1  

and
with 500 data point.

rnorm(n=500, m=1, sd=1)

But, I am confusing with how to generate a normal distribution

with  

expected
min and max. I expect to hear your directions.

Thanks in advance.

Best,
Jian-Feng,

      [[alternative HTML version deleted]]

Well, but the original poster also refers to 0.2 and 0.8 as "expected 
min and max", in which case we are back to a joke...

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Mao Jianfeng
Sent: Thursday, April 28, 2011 12:02 PM
To: r-help at r-project.org
Subject: [R] how to generate a normal distribution with mean=1, min=0.2, max=0.8

Dear all,

This is a simple probability problem. I want to know, How to generate 
a normal distribution with mean=1, min=0.2 and max=0.8?

I know how the generate a normal distribution of mean = 1 and sd = 1 
and with 500 data point.

rnorm(n=500, m=1, sd=1)

But, I am confusing with how to generate a normal distribution with 
expected min and max. I expect to hear your directions.

Thanks in advance.

Best,
Jian-Feng,

On Fri, 29 Apr 2011, Giovanni Petris wrote:

Well, but the original poster also refers to 0.2 and 0.8 as  
"expected min and max", in which case we are back to a joke...

Well, he is a lot better with English than I am with Mandarin.  He  
seemed to like the truncated normal answers, so we'll let those be  
his answers.

It is possible to choose parameters for a normal distribution with  
500 observations such that the expected value of the maximum is .8  
and the expected value of the minimum is .2.  Obviously, the mean  
would be .5, not 1, but what would the variance then have to be to  
provide the correct expected max and min?  That's another legitimate  
question.

On Apr 29, 2011, at 1:29 PM, Mike Miller wrote:

On Fri, 29 Apr 2011, Giovanni Petris wrote:

Well, but the original poster also refers to 0.2 and 0.8 as "expected min 
and max", in which case we are back to a joke...

Well, he is a lot better with English than I am with Mandarin.  He seemed 
to like the truncated normal answers, so we'll let those be his answers.

It is possible to choose parameters for a normal distribution with 500 
observations such that the expected value of the maximum is .8 and the 
expected value of the minimum is .2.  Obviously, the mean would be .5, 
not 1, but what would the variance then have to be to provide the 
correct expected max and min?  That's another legitimate question.

You would need to specify an N since the expected first and last order 
statistic would decrease/increase with increasing N.