st: simulate consequences of selection bias 101

[Thomas Gschwend <gschwend@uni-mannheim.de>]

Dear all,
prompted by a student‘s question when teaching about the virtues of 
selection bias I would like to simulate some data which fulfills the 
following requirements, whereby Y = b0 + b1*X

1)	When regressing Y on X (for the full sample)
b1 = -.5 and significantly < 0

2)	When regressing Y on X (for a subsample, say for Y > 10)
b1 = +2 and significantly > 0

I am not sure how to do simulate data that fulfills both requirements.

Any help is greatly appreciated.

Thomas
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