Correlation Confidence Intvls
$0.99
8.1for iPhone, iPad and more
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About Correlation Confidence Intvls
Correlation is a quantitative tool commonly used by researchers to separate data sets into independent subgroups. Hypothesis testing determines whether or not the subgroups are numerically distinct. The degree to which the researcher can say the subgroups are distinct depends upon the overlap between the subgroups measured by the confidence interval estimates. The confidence interval estimates reflect the reality that there are errors in all quantitative estimates.
If correlation estimates were normally distributed, estimates of confidence intervals would be straightforward. However, correlation estimates are bound within the range of –1.0 to +1.0. The common technique devised by R.A. Fisher involves a nonlinear transformation of correlation functions into random variables that are approximately normal. The technique is known as Fisher's z-transformation and is formally expressed as ρ = tanh(z), where tanh( ) is the hyperbolic tangent function.
More simply, the transformed standard error, z, is defined as z = (1/2) ln[ (1 + ρ) / (1 – ρ) ]. The variance is a function of the number of paired samples in the sets being correlated and is defined as var(z) = 1 / (n – 8/3).
Thus, for example, the 95% confidence interval around a correlation estimate would be from (z – 1.96 σ) to (z + 1.96 σ) where σ = sqrt( 1/ (n – 8/3) ).
The iPad version allows you to add, retrieve, reorder, or delete data sets. Also, you may email, send via texting, and print data and results.
If correlation estimates were normally distributed, estimates of confidence intervals would be straightforward. However, correlation estimates are bound within the range of –1.0 to +1.0. The common technique devised by R.A. Fisher involves a nonlinear transformation of correlation functions into random variables that are approximately normal. The technique is known as Fisher's z-transformation and is formally expressed as ρ = tanh(z), where tanh( ) is the hyperbolic tangent function.
More simply, the transformed standard error, z, is defined as z = (1/2) ln[ (1 + ρ) / (1 – ρ) ]. The variance is a function of the number of paired samples in the sets being correlated and is defined as var(z) = 1 / (n – 8/3).
Thus, for example, the 95% confidence interval around a correlation estimate would be from (z – 1.96 σ) to (z + 1.96 σ) where σ = sqrt( 1/ (n – 8/3) ).
The iPad version allows you to add, retrieve, reorder, or delete data sets. Also, you may email, send via texting, and print data and results.
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What's New in the Latest Version 8.1
Last updated on Apr 23, 2022
Old Versions
- Corrected colors in Dark mode.
- Fixed problem that prevented sharing of PDF output.
- Various GUI tweaks.
- Fixed problem that prevented sharing of PDF output.
- Various GUI tweaks.
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Version History
8.1
Apr 23, 2022
- Corrected colors in Dark mode.
- Fixed problem that prevented sharing of PDF output.
- Various GUI tweaks.
- Fixed problem that prevented sharing of PDF output.
- Various GUI tweaks.
8.0
Feb 4, 2022
- Update to accommodate latest versions of iOS.
- Some code simplifications.
- Removed links to Facebook and Twitter.
- Various GUI tweaks.
- Some code simplifications.
- Removed links to Facebook and Twitter.
- Various GUI tweaks.
7.3
Dec 20, 2018
- Updates to newer versions of iOS.
- Various code changes.
- Various code changes.
7.2
Oct 1, 2015
- Changes to adapt to iOS 9, mostly involving fonts.
7.1
Jul 10, 2015
- Bug fixes in iPhone version related to +/– correlation coefficient data entry and clearing of data.
- Added Facebook and Twitter links.
- Code improvements.
- GUI changes.
- Added continuous increase or decrease in confidence interval setting in iPad version.
- Added Facebook and Twitter links.
- Code improvements.
- GUI changes.
- Added continuous increase or decrease in confidence interval setting in iPad version.
4.1
Oct 5, 2014
- Updated for iOS 8 and iPhone 6.
- Minor GUI tweaks.
- Updated graphing engine.
- Minor GUI tweaks.
- Updated graphing engine.
4.0
Mar 5, 2014
- iPad version now adds email, text message, and print capability. A PDF report at a resolution of 72 dpi is available for sharing.
- Streamlined and improved source code.
- GUI improvements.
- Streamlined and improved source code.
- GUI improvements.
3.0
Nov 8, 2013
- Major rewrite and redesign for iOS 7.
- Bug fixes.
- Bug fixes.
2.0
Aug 20, 2013
- Major revision that includes the option of adding data sets, retrieving saved sets, and deleting or reordering the saved sets.
1.2
Apr 29, 2013
- Fixed bug that allowed graph to be moved around with a finger gesture.
1.1
Apr 1, 2013
- The behavior of the "info" and "clear" buttons have been modified to avoid unanticipated behaviors.
1.0
Mar 20, 2013
Correlation Confidence Intvls FAQ
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Check the following list to see the minimum requirements of Correlation Confidence Intvls.
iPhone
Requires iOS 12.4 or later.
iPad
Requires iPadOS 12.4 or later.
iPod touch
Requires iOS 12.4 or later.
Correlation Confidence Intvls supports English