What does fold change mean?

If a research study describes something as having a 0.6 fold change. Does that mean it is higher or lower?

 

That must be in the paper.

 

The number n, after a 0.6 fold change, is n * 0.6

 

This seems to explain it:

https://www.researchgate.net/post/what_fold_change_resistance_factor_tells_about_drug_resistance

ETA: Just realised I missed the point! A 2-fold change is a 2x, or 2 times, change. Replace 'fold' for multiply sign. As others have said above. I was thinking there was something medical-speak about "fold change" .

 

I don't think this is at all clear. A 0.6 fold change could be a change to 60% or to 166% or even to 160% or 40% as far as I can see. Nobody normally says this. Unless it is some special technical term in a particular area it sounds like half-baked usage.

 

But a tenfold change can be to 10%. We often say change by an order of magnitude - when it is already assumed which way.

They probably mean change to 60% but why not say so? We normally say a 40% decrease.

 

Never having had any occasion to refer to a fold change in real life, for a long time I assumed it was 2^x, where x was the number of "folds," as in folding a piece of paper equally. So, three fold of something would be 8 times the original, because, in my mind, if you folded a piece of paper equally 3 times you produced 2^3 subdivisions, i.e. 8.


Sigh. Another beautiful hypothesis slayed by an ugly fact.

 

Start at zero, or baseline of whatever you are testing about.

"Fold" means x or multiplied by x.

So starting at zero, increase by 0.6x.