Confidence interval on Standard deviation

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Discussion Overview

The discussion revolves around calculating the confidence interval for the standard deviation using the chi-square distribution. Participants explore the appropriate degrees of freedom and tools available for this calculation, focusing on a specific example with a sample size of 500 and a sample standard deviation of 3.

Discussion Character

  • Technical explanation, Homework-related

Main Points Raised

  • One participant states that the confidence interval for standard deviation can be found using the chi-square distribution and questions the correct degrees of freedom to use.
  • Another participant clarifies that the degrees of freedom is the sample size minus one (499) but notes that this is not required by the online tool they mentioned.
  • A participant expresses a specific interest in the confidence interval for standard deviation rather than the mean, indicating a need for more targeted resources.
  • Another participant provides a tool that calculates the confidence interval for standard deviation, reporting a range of 2.82 to 3.20, and references a specific example from an external site that gives a formula for the 95% confidence interval.
  • It is reiterated that the degrees of freedom remains 499 in the context of the provided examples.

Areas of Agreement / Disagreement

Participants generally agree on the method of using the chi-square distribution for calculating the confidence interval for standard deviation, but there is some uncertainty regarding the application of degrees of freedom and the specific tools available for this calculation.

Contextual Notes

There is a lack of clarity regarding the specific tools that provide the confidence interval for standard deviation, and the discussion does not resolve the potential differences in interpretations of degrees of freedom in this context.

Who May Find This Useful

Readers interested in statistical methods for calculating confidence intervals, particularly in the context of standard deviation, may find this discussion relevant.

iVenky
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I read that confidence interval on standard deviation can be found using chi-square distribution. If I have a sample size N=500, and sample standard deviation= 3 with mean=0, and I need a 95% confidence, I wasn't sure what to set for degrees of freedom in chi-square formula. Is the degrees of freedom same as the sample size? Is there an online-tool that can do the math for you if I enter the values?
 
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You can calculate your confidence interval with this tool:
Confidence Interval

The degrees of freedom is you sample size minus one (499), but that is not required by this tool.
 
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Likes   Reactions: iVenky
Hi,

Thanks for the reply, but I am interested in confidence interval of the standard deviation rather than the mean. The link that you mentioned doesn't contain the confidence interval for standard deviation
 
Thank you very much!
 

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