Occurrences Report

Context, Background, and Motivation

  • Occurrences refer to the number of observations in a cell of a Probability Table or a Conditional Probability Table.

  • The number of cells in a Conditional Probability Table is a function of the following parameters:

    • The number of Parent Nodes.

    • The number of Node States of the Parent Nodes.

    • The number of Node States of the Child Nodes.

  • The following example with one Parent Node (Age, measured in years) and one Child Node (BMI, i.e., Body Mass Index, measured in kgm2\frac{{kg}}{{{m^2}}}) illustrates this with numbers:

  • Here, Age is discretized into 4 states and BMI into 6 for a total of 48 cells in the table associated with BMI.

  • The numbers in each cell are counts of observations or Occurrences. In our case, each Occurrence represents one person from the sample of 200 individuals.

  • For instance, the Occurrence table associated with BMI states that Count(BMIโ‰ค20 | Ageโ‰ค30)=2. So, we have only two Occurrences of that particular condition, i.e., only two individuals who are 30 years old or younger have a BMI of 20 or lower.

  • To create a Bayesian network, BayesiaLab needs to translate the Occurrences in each cell into probabilities.

  • However, with a small number of Occurrences, that can become an issue.

  • We have repeatedly referenced a rule of thumb, which says that we should have a minimum of 5 Occurrences per cell to estimate a Probability Table or Conditional Probability Table reliably.

  • In our example, several cells fall below the recommended minimum.

  • Such deficiencies are easy to recognize in a small example, but in more complex networks, it can be difficult to spot such weaknesses.

  • That is the motivation for the Occurrence Report. It displays all tables in a network and visually highlights potentially problematic cells with low Occurrences.

Usage

  • Select the nodes you want to include in the Occurrences Report. I none are selected, the analysis will be performed on all nodes.

  • Select Main Menu > Network > Reports > Reports> Occurrences to create the Occurrences Report.

  • The Occurrence Report opens up and shows all Probability Tables and Conditional Probability Tables.

  • The fields in the report are color-coded to highlight potential issues:

    • Cells with 0 Occurrences are marked in red.

    • Cells with 5 Occurrences are marked in yellow. This is generally considered the minimum number of Occurrences.

    • Cells with 40 or more Occurrences are marked in green.

  • Furthermore, the Occurrence Report calculates the mean number of Occurrences for each row in all Probability Tables and Conditional Probability Tables.

  • If the mean value of any row in any of the nodes drops below the threshold of 5, the corresponding nodes are called out at the top of the report.

  • The affected nodes in the Graph Panel are also marked with the information icon .

Last updated

Logo

Bayesia USA

info@bayesia.us

Bayesia S.A.S.

info@bayesia.com

Bayesia Singapore

info@bayesia.com.sg

Copyright ยฉ 2024 Bayesia S.A.S., Bayesia USA, LLC, and Bayesia Singapore Pte. Ltd. All Rights Reserved.