Sample size required to estimate population variance

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Sample size required to estimate population variance

R help mailing list-2
Colleagues,
Can anyone suggest a package or code which might help me calculate the minimum sample size required to estimate the population variance? I can do this in Minitab but I'd rather do this in R.
Thomas Subia
        [[alternative HTML version deleted]]

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Re: Sample size required to estimate population variance

Richard O'Keefe-2
Does this help?
https://www.r-bloggers.com/computing-sample-size-for-variance-estimation/

On Wed, 3 Jul 2019 at 10:23, Thomas Subia via R-help <[hidden email]>
wrote:

> Colleagues,
> Can anyone suggest a package or code which might help me calculate the
> minimum sample size required to estimate the population variance? I can do
> this in Minitab but I'd rather do this in R.
> Thomas Subia
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> 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.
>

        [[alternative HTML version deleted]]

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Re: Sample size required to estimate population variance

Rui Barradas
In reply to this post by R help mailing list-2
Hello,Maybe I'm not understanding but to compute the sample variance you need at least 2 data points? The ML estimator can be computed with just 1 but it will be zero.Hope this helps,Rui Barradas Enviado a partir do meu smartphone Samsung Galaxy.-------- Mensagem original --------De: Thomas Subia via R-help <[hidden email]> Data: 02/07/2019  23:23  (GMT+00:00) Para: [hidden email] Assunto: [R] Sample size required to estimate population variance Colleagues,Can anyone suggest a package or code which might help me calculate the minimum sample size required to estimate the population variance? I can do this in Minitab but I'd rather do this in R.Thomas Subia [[alternative HTML version deleted]][hidden email] mailing list -- To UNSUBSCRIBE and more, seehttps://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
        [[alternative HTML version deleted]]

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Re: Sample size required to estimate population variance

Rui Barradas
Hello,

Sorry for the HTML, I hadn't realised that my cellphone was not  
sending in plain text.

Rui Barradas







Citando ruipbarradas <[hidden email]>:

> Hello,Maybe I'm not understanding but to compute the sample variance  
> you need at least 2 data points? The ML estimator can be computed  
> with just 1 but it will be zero.Hope this helps,Rui Barradas Enviado  
> a partir do meu smartphone Samsung Galaxy.-------- Mensagem original  
> --------De: Thomas Subia via R-help <[hidden email]> Data:  
> 02/07/2019  23:23  (GMT+00:00) Para: [hidden email] Assunto:  
> [R] Sample size required to estimate population variance  
> Colleagues,Can anyone suggest a package or code which might help me  
> calculate the minimum sample size required to estimate the  
> population variance? I can do this in Minitab but I'd rather do this  
> in R.Thomas Subia [[alternative HTML version  
> deleted]][hidden email]  
> mailing list -- To UNSUBSCRIBE and more,  
> seehttps://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the  
> posting guide http://www.R-project.org/posting-guide.htmland provide  
> commented, minimal, self-contained, reproducible code.
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> 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.

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Re: Sample size required to estimate population variance

R help mailing list-2
In reply to this post by R help mailing list-2
On Tue, 2 Jul 2019 22:23:18 +0000 (UTC)
Thomas Subia via R-help <[hidden email]> wrote:

> Colleagues,
> Can anyone suggest a package or code which might help me calculate
> the minimum sample size required to estimate the population variance?
> I can do this in Minitab but I'd rather do this in R. Thomas Subia

You want to look into the capabilities of the pwr package.  This page
offers some information:

https://www.statmethods.net/stats/power.html

JWDougherty

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Re: Sample size required to estimate population variance

R help mailing list-2
 Thanks for the suggestion but I'm not sure that it answers my original question.I need to know how many samples I need to collect to collect in order to estimate the sample size needed to achieve a specific margin of error for confidence intervals for the population variance. I'm not sure whether the pwr package does that.


    On Thursday, July 4, 2019, 4:31:44 PM PDT, John <[hidden email]> wrote:  
 
 On Tue, 2 Jul 2019 22:23:18 +0000 (UTC)
Thomas Subia via R-help <[hidden email]> wrote:

> Colleagues,
> Can anyone suggest a package or code which might help me calculate
> the minimum sample size required to estimate the population variance?
> I can do this in Minitab but I'd rather do this in R. Thomas Subia

You want to look into the capabilities of the pwr package.  This page
offers some information:

https://www.statmethods.net/stats/power.html

JWDougherty
 
        [[alternative HTML version deleted]]

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Re: Sample size required to estimate population variance

S Ellison-2
>  Thanks for the suggestion but I'm not sure that it answers my original
> question.I need to know how many samples I need to collect to collect in
> order to estimate the sample size needed to achieve a specific margin of
> error for confidence intervals for the population variance. I'm not sure
> whether the pwr package does that.

You could consider the case of 50% power, though that'd not be exact for asymmetry.

But if this is a simple univariate data set, it sounds like messing around with chi-squared quantiles and uniroot ought to work. Exactly how are you calculating your confidence limits and which one (upper or lower) needs to be of a specific size?


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