26 October 2012

Ready Reckoners


If you encounter problems using the following calculators, notice errors in their operation, or would like to suggest improvements, please send details using the contact form. Reference sources used in the development of the calculators are given at the bottom of this page.


Blank data cells are interpreted as zero, and coloured cells display results. Enter data into input cells and click button for results.

Calculate interim EBV and accuracy figures using sire and dam figures alone

An interim EBV and accuracy can be calculated for calves that have no performance records using sire and dam EBVs and accuracies. By comparing interim EBVs and accuracies with published EBVs and accuracies, users of this calculator can determine the impact that field measurements have had on an animal's EBV.

INPUT DATA Sire Dam
EBVs:
Accuracy: % %

RESULTS Progeny  
EBV:  
Accuracy: %  
   


Conversion to and from Breedplan EBV accuracy, US EPD accuracy, and true accuracy

True accuracy is the amount by which the prediction error margin, also known as confidence range, for an EBV is reduced as a result of performance recording of an animal and its relatives. For example, an EBV with true accuracy of 50% indicates that the prediction error margin for the EBV is half that if it had zero accuracy, and a true accuracy of 80% means that the prediction error margin is reduced by 80%.

This linear method of representing accuracy information is used in North American breeding evaluations (EPDs). However, Breedplan uses a method that exaggerates the precision of EBVs. For example, a Breedplan EBV accuracy figure of 80% is equivalent to a North American EPD accuracy of 0.4 and a true accuracy of 40%!

The following two calculators convert EBV accuracy to the equivalent North American EPD accuracy and true accuracy, and vice versa.

Convert Australian EBV accuracy figure to the US EPD equivalent and true accuracy.

INPUT DATA      
  Australian EBV Accuracy: %  

RESULTS      
Equivalent North American EPD accuracy: True accuracy: %
     

Convert US EPD accuracy figure to Australian EBV equivalent and true accuracy.

INPUT DATA      
  North American EPD Accuracy:  

RESULTS      
Equivalent Australian EBV Accuracy: % True accuracy: %
     

References

The equations used in the above calculators are derivations of those given on pages 72 and 151 in the US Guidelines for Uniform Beef Improvement Programs, 9th Edition (2010), and adapted using EBV accuracy, prediction error variance and trait variance relationships used by ABRI. The US Guidline document is accessible on the Beef Improvement Federation website at www.beefimprovement.org.