Repository of Reproducible Computations

Free Statistics

of Irreproducible Research!

Author's title

Author

*The author of this computation has been verified*

R Software Module

rwasp_hypothesisvariance3.wasp

Title produced by software

Testing Variance - Confidence Intervals for Sample Variance

Date of computation

Thu, 13 Nov 2008 09:16:28 -0700

Cite this page as follows

Statistical Computations at FreeStatistics.org, Office for Research Development and Education, URL https://freestatistics.org/blog/index.php?v=date/2008/Nov/13/t12265930680dwrohsw8epvzt0.htm/, Retrieved Sun, 19 May 2024 09:24:58 +0000

Statistical Computations at FreeStatistics.org, Office for Research Development and Education, URL https://freestatistics.org/blog/index.php?pk=24671, Retrieved Sun, 19 May 2024 09:24:58 +0000

QR Codes:

Paste this QR Code to cite your computation.

Original text written by user:

IsPrivate?

No (this computation is public)

User-defined keywords

Estimated Impact

154

Family? (F = Feedback message, R = changed R code, M = changed R Module, P = changed Parameters, D = changed Data)

F       [Testing Variance - Confidence Intervals for Sample Variance] [question 2 pork] [2008-11-13 16:16:28] [f7fbcd402030df685d3fe4ce577d7846] [Current]

Feedback Forum

2008-11-16 14:08:34 [Julie Govaerts] [reply] 
Gebruikte techniek: Testing Mean with known Variance - p-value 
p value = probability = waarschijnlijkheid 
 
De type I error (= alfafout, de kans dat we ons vergissen bij het verwerpen van de nulhypothese) moet je zelf bepalen (hier bepaald door het management). 
De p-value is de kans dat het te wijten is aan toeval. De p-value is dus de werkelijke kans dat u zich vergist. 
 
De werkelijk kans dat we ons vergissen als we een klacht indienen, is 41% (p-value). Zelf hadden we de kans dat we ons vergissen bewust op 5% bepaald. 
De werkelijke kans dat we ons vergissen is dus veel groter dan de kans die we ons hadden voorgenomen.  
=> We mogen de nulhypothese dus zeker niet verwerpen aangezien de p-value groter is dan de alfafout. 
 
Nogmaals blijkt dat het verschil tussen de 15% en de 15.46% te wijten is aan toeval. 
 
we maken hier gebruik van een 1 sided test omdat het enkel mogelijk is dat er teveel vet in het vlees zit = omdat we een vermoeden hebben
2008-11-17 14:04:32 [Hundra Smet] [reply] 
de student gebruikte heir alweer een foute methode: Testing Variance - Confidence Intervals for Sample Variance ipv Testing Mean with known Variance. ook de 1 zinnige conclusie is fout. 
 
je hebt al een vermoeden, daarom kan de fraude slechts in 1 richting gaan (= teveel vet voor een financ. voordeel te bekomen).  
we zien dat de one tailed p value slechts 41% is (geen 82,72% zoals ik zei in de conclusie), dit is de kans dat je je vergist bij het verwerpen van de nulhypothese. (en dus niet de kans op een onrechtvaardige klacht) 
 
we zien ook dat de p value groter is dan de alfa fout; dit wil zeggen dat we de nulhypothese niet gaan verwerpen. (het verschil hiertussen is aan toeval te wijten) 

Post a new message

Summary of computational transaction
Raw Input	view raw input (R code)
Raw Output	view raw output of R engine
Computing time	1 seconds
R Server	'Gwilym Jenkins' @ 72.249.127.135

\begin{tabular}{lllllllll}
\hline
Summary of computational transaction \tabularnewline
Raw Input & view raw input (R code)  \tabularnewline
Raw Output & view raw output of R engine  \tabularnewline
Computing time & 1 seconds \tabularnewline
R Server & 'Gwilym Jenkins' @ 72.249.127.135 \tabularnewline
\hline
\end{tabular}
%Source: https://freestatistics.org/blog/index.php?pk=24671&T=0

[TABLE]
[ROW][C]Summary of computational transaction[/C][/ROW]
[ROW][C]Raw Input[/C][C]view raw input (R code) [/C][/ROW]
[ROW][C]Raw Output[/C][C]view raw output of R engine [/C][/ROW]
[ROW][C]Computing time[/C][C]1 seconds[/C][/ROW]
[ROW][C]R Server[/C][C]'Gwilym Jenkins' @ 72.249.127.135[/C][/ROW]
[/TABLE]
Source: https://freestatistics.org/blog/index.php?pk=24671&T=0

Globally Unique Identifier (entire table): ba.freestatistics.org/blog/index.php?pk=24671&T=0

As an alternative you can also use a QR Code:

The GUIDs for individual cells are displayed in the table below:

Summary of computational transaction
Raw Input	view raw input (R code)
Raw Output	view raw output of R engine
Computing time	1 seconds
R Server	'Gwilym Jenkins' @ 72.249.127.135

Testing Variance - Confidence Intervals for Sample Variance
Sample size	320
Null hypothesis (H0)	4.8
Confidence interval	0.95
Type of Interval	Left tail	Right tail
Two-sided confidence interval at 0.95	4.08398114582379	5.57300042302749
Left one-sided confidence interval at 0.95	4.19241479848094	+inf
Right one-sided confidence interval at 0.95	0	5.44179137186305
more information about confidence interval

\begin{tabular}{lllllllll}
\hline
Testing Variance - Confidence Intervals for Sample Variance \tabularnewline
Sample size & 320 \tabularnewline
Null hypothesis (H0) & 4.8 \tabularnewline
Confidence interval & 0.95 \tabularnewline
Type of Interval & Left tail & Right tail \tabularnewline
Two-sided confidence interval at  0.95 & 4.08398114582379 & 5.57300042302749 \tabularnewline
Left one-sided confidence interval at  0.95 & 4.19241479848094 & +inf \tabularnewline
Right one-sided confidence interval at  0.95 & 0 & 5.44179137186305 \tabularnewline
more information about confidence interval \tabularnewline
\hline
\end{tabular}
%Source: https://freestatistics.org/blog/index.php?pk=24671&T=1

[TABLE]
[ROW][C]Testing Variance - Confidence Intervals for Sample Variance[/C][/ROW]
[ROW][C]Sample size[/C][C]320[/C][/ROW]
[ROW][C]Null hypothesis (H0)[/C][C]4.8[/C][/ROW]
[ROW][C]Confidence interval[/C][C]0.95[/C][/ROW]
[ROW][C]Type of Interval[/C][C]Left tail[/C][C]Right tail[/C][/ROW]
[ROW][C]Two-sided confidence interval at  0.95[/C][C]4.08398114582379[/C][C]5.57300042302749[/C][/ROW]
[ROW][C]Left one-sided confidence interval at  0.95[/C][C]4.19241479848094[/C][C]+inf[/C][/ROW]
[ROW][C]Right one-sided confidence interval at  0.95[/C][C]0[/C][C]5.44179137186305[/C][/ROW]
[ROW][C]more information about confidence interval[/C][/ROW]
[/TABLE]
Source: https://freestatistics.org/blog/index.php?pk=24671&T=1

Globally Unique Identifier (entire table): ba.freestatistics.org/blog/index.php?pk=24671&T=1

As an alternative you can also use a QR Code:

The GUIDs for individual cells are displayed in the table below:

Testing Variance - Confidence Intervals for Sample Variance
Sample size	320
Null hypothesis (H0)	4.8
Confidence interval	0.95
Type of Interval	Left tail	Right tail
Two-sided confidence interval at 0.95	4.08398114582379	5.57300042302749
Left one-sided confidence interval at 0.95	4.19241479848094	+inf
Right one-sided confidence interval at 0.95	0	5.44179137186305
more information about confidence interval

Parameters (Session):

par1 = 320 ; par2 = 4.8 ; par3 = 0.95 ;

Parameters (R input):

par1 = 320 ; par2 = 4.8 ; par3 = 0.95 ;

R code (references can be found in the software module):

par1<-as.numeric(par1)
par2<-as.numeric(par2)
par3<-as.numeric(par3)
df <- par1 - 1
halfalpha <- (1 - par3) / 2
ua <- qchisq(halfalpha,df) * par2 / df
ub <- qchisq(1-halfalpha,df) * par2 / df
ua
ub
ul <- qchisq(1-par3,df) * par2 / df
ul
ur <- qchisq(par3,df) * par2 / df
ur
load(file='createtable')
a<-table.start()
a<-table.row.start(a)
a<-table.element(a,hyperlink('ht_variance.htm','Testing Variance - Confidence Intervals for Sample Variance','learn more about Statistical Hypothesis Testing about the Variance'),3,TRUE)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,'Sample size',header=TRUE)
a<-table.element(a,par1,2)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,'Null hypothesis (H0)',header=TRUE)
a<-table.element(a,par2,2)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,'Confidence interval',header=TRUE)
a<-table.element(a,par3,2)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,'Type of Interval',header=TRUE)
a<-table.element(a,'Left tail',header=TRUE)
a<-table.element(a,'Right tail',header=TRUE)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,paste('Two-sided confidence interval at ',par3), header=TRUE)
a<-table.element(a,ua)
a<-table.element(a,ub)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,paste('Left one-sided confidence interval at ',par3), header=TRUE)
a<-table.element(a,ul)
a<-table.element(a,'+inf')
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a,paste('Right one-sided confidence interval at ',par3), header=TRUE)
a<-table.element(a,'0')
a<-table.element(a,ur)
a<-table.row.end(a)
a<-table.row.start(a)
a<-table.element(a, hyperlink('ht_variance.htm#ex3', 'more information about confidence interval','example'),3,TRUE)
a<-table.row.end(a)
a<-table.end(a)
table.save(a,file='mytable.tab')

Free Statistics

Description of Statistical Computation

Tree of Dependent Computations

Dataset

Tables (Output of Computation)

Figures (Output of Computation)

Input Parameters & R Code