Machine Learning

Do Not Use Random Guessing As Your Baseline Classifier

Last Updated on September 25, 2019

I recently received the following question via email:

Hi Jason, quick question. A case of class imbalance: 90 cases of thumbs up 10 cases of thumbs down. How would we calculate random guessing accuracy in this case?

We can answer this question using some basic probability (I opened excel and typed in some numbers).

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Note, for a more detailed tutorial on this topic, see:

Don't Use Random Guessing As Your Baseline Classifier

Don’t Use Random Guessing As Your Baseline Classifier
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Let’s say the split is 90%-10% for class 0 and class 1. Let’s also say that you will guess randomly using the same ratio.

The theoretical accuracy of random guessing on a two-classification problem is: