# What's an example of a situation in which it makes sense to assume random slopes but a fixed intercept?

I'm referring to multilevel modelling. Field (2013) writes:

It’s worth noting that it would be unusual in reality to assume random slopes without also assuming random intercepts, because variability in the nature of the relationship (slopes) would normally create variability in the overall level of the outcome variable (intercepts). Therefore, if you assume that slopes are random you would normally also assume that intercepts are random.

Can anyone think of an example (preferably, but not necessarily, from an actual analysis) in which it was appropriate to assume random slopes but a fixed intercept? Why was it appropriate in that case?

Field, Andy. Discovering statistics using IBM SPSS statistics. Sage, 2013.

• What is Field (2014)? May 6, 2015 at 21:59
• Sorry, forgot to put the citation in. May 6, 2015 at 22:01