Hi there,
I'd like to include education as a control in my analysis. I am using the ESS, so my data is cross-national. For better comparison across different educational systems I'd like to include a continuous variable based on 'years in education'. I like the following operationalisation:

"Education is assessed continuously to enhance the comparability of educational systems between countries (Berigan and Irwin, 2011). The impact of outliers is minimized by equalizing all scores higher than the country-year-specific mean plus 3 standard deviations."

Could anyone tell me how to code it ?
My first thought was using a foreach-loop somehow but I am a little overwhelmed on how to do it, especially, on how to limit the values to 3 sd from the mean....
Thanks a lot in advance!!