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Understanding Viral Load Assays for Cytomegalovirus and Epstein-Barr Virus


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Log vs Fold

Slide 23

March 2010

So how do changes on the integer scale compare to changes on the log scale? In this table, I demonstrate 3 pairs of numbers. The black text is integer values, and the blue text is log values. The middle column shows the fold difference between the integer values. For example, in the first row, 100 is 10 fold higher than 10. The column on the right shows the difference of the log numbers. The log of 100 is 2, and the log of 10 is 1. Thus, the difference between those values is 1. In the middle row, you can see that a 3 fold change is about half a log difference. This is a helpful relationship to remember. Finally, in the third row, we can see that a 2-fold difference, in this case 20,000 to 40,000 is a difference of about 0.3 log.

Log vs Fold


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