Don't use the variable name "values" in the examples

[mirams]

values is just the same as saying numbers - which isn't a very helpful variable name :-)

It means at least two distinct things that are not the same in here: https://github.com/pints-team/pints/blob/master/examples/stats/custom-model.ipynb

Either simulated_data or model_output or whatever would be better, or even just y to match the maths at the top for some of them.