effectus: Cause & Effect Library

effectus tells you which minority of causes provokes which majority of effects.


You provide it with a series of numbers. It tells you whether a pareto distribution is present.

Use it in Python, evaluate CSV files or your current selection within Excel from the command line (for the last two no programming skills are required).

effectus employs the entropy based model by Grosfeld-Nir, Ronen and Kozlovsky.


Mean, Median and Most likely value regularly hide that a minority of causes provokes a majority of effects.

The Fallacy of the Arithmetic Mean explains the situation in-depth.

Install it

$ pip3 install effectus

Use it

Wrap your values in the class Effects:

>>> from effectus import Effects
>>> Effects([789, 621, 109, 65, 45, 30, 27, 15, 12, 9])
<pareto present [0.707]: 1/5 causes => 4/5 effects [total ∆: 1.9 % points]>

Finished. We have a pareto distribution present: One fifth makes up for four fifths of results.

Interested in a in-depth look at all core functions? Then the Tutorial might be something for you.