On the Nonadditivity of Correlation Coefficients Part 1: Pearson and Spearman Coefficients


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This is Part 1 of a tutorial series on the nonadditivity of correlation coefficients. We demonstrate why it is not possible to arithmetically add, subtract, and average Pearson’s r or Spearman’s rs.

The article is available at


07-04-2017 update: In page 1 the line for the Beta1 should read “is the slope of a simple linear regression model”. My fault. Fixed today along with few other nuances.

Enjoy it!

t,p, & Effect Size Estimator


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This is a new Minerazzi tool, available now at


This tool estimates t-scores from p-values and vice versa for a given number of degrees of freedom υ. Just enter a (t,υ) or (p,υ) pair and this tool will solve for the missing term.

The tool also estimates the statistics that one would obtain if the computed estimates correspond to a set of paired variables (x, y), or to effect sizes from any two samples of same sizes (n1 and n2); i.e. samples with same degrees of freedom (υ1 and υ2).

The tool’s page lists some interesting exercises and good references for effect size conversions and meta-analysis in general. Enjoy it!


Student’s t Table Generator


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This is a new tool available now at


This tool allows you to easily generate a customized table of Student’s t-values.

That is done by iteratively calling (i.e., looping) the very same algorithm that we use for our t-values Calculator.

This tool comes handy when you don’t have statistical t-tables around or are working with p and t values, or degrees of freedom, not available from such tables. Avoid pausing a problem for annoying linear interpolation workarounds!

Meta-Analysis Miner


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This is a new miner available now at


Find resources relevant to meta-analysis, effect sizes, and power analysis with this Minerazzi miner.

Build curated collections on these subjects.

The miner includes Bing and Google RSS News channels powered by our SPP tool.

t-values Calculator for Student’s t Hypothesis Testing


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The t-values Calculator is a new Minerazzi tool, available now at


The tool works by computing, through numerical approximation methods, the Inverse Cumulative Distribution Function or ICDF (also known as the Quantile Function, QF) of the Student’s t Distribution.

This new tool complements our p-values Calculator, described in


and available at


The t-values calculator comes handy when you don’t have around statistical t-tables or want to t-testing at confidence levels and degrees of freedom not listed in such tables. In fact, with a small change to the script, we can build another tool for the generation of t-tables at any confidence level and degrees of freedom as specified by a user.

Both tools will eventually be used to provide a third tool: The t-p Transformation tool that, as the name suggests, transforms CDF (t-to-p) into ICDF (p-to-t) results and vice versa.



p-values Calculator for Student’s t Hypothesis Testing


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The p-Values Calculator is a new Minerazzi tool that is available now at


Submitting a Student’s t value and degrees of freedom returns a p-value. This is a great tool for Student’s t hypothesis testing.

The tool works by numerically approximating the CDF (Cumulative Distribution Function). This is the integral of the PDF (Probability Distribution Function) of the Student’s t Distribution. The theory behind these calculations along with valuable references are given in the tool’s page.


The reverse process, computing t from a p-value is possible by inverting the CDF to compute the Quantile Function (QF), also known as the inverse CDF. Our (soon to be released) t-p Transformations tool computes both the CDF (t-to-p) and QF (p-to-t).

Updating Several Miners


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We have reindexed the following miners:




Memory Based Reasoning in AI


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This is a nice course on Memory Based Reasoning in AI taught by Dr. Deepak Khemani and Dr. Sutanu Chakraborti at the Department of Computer Science & Engineering, Indian Institute of Technology Madras, Chennai, India. See


Happy to see that the following readings from the course are based on two articles we published long time ago at Mi Islita.com, now a search engine site about Puerto Rico resources.

Reading #10
Vector Space Models

Reading #11

Python Search Engine


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Here is a python-based search engine with an implementation inspired on one of our papers at the old Mi Islita.com site, now a search engine on Puerto Rico.


This module replicates the miislita vector spaces from
"A Linear Algebra Approach to the Vector Space Model -- A Fast Track Tutorial"
by Dr. E. Garcia...

Great and positive accomplishment!

That tutorial is no longer at miislita.com, but was long ago moved to minerazzi.com. Find it here:


For other resources do a search for python in our IR miner at


For inquiries about that implementation, contact its author.

For other inquiries, applications, suggestions, drop me a line.

PS. Please note that Nullege.com itself is a search engine for finding python code. Here is a good example: http://nullege.com/codes/search/wx.calendar.CalendarCtrl