No. Absolutely not . @Rick_SAS wrote a wonderful blog "Simpson's Paradox" to explain this problem. https://blogs.sas.com/content/iml/2023/03/27/simpsons-paradox.html     Suppose X stands for income per month, Y stands for the probability of default , From all the data, you could see the linear decreasing relationship between X and Y. But if you take into account AGE variable, you would see the reverse result . Surprise ? So you can't constraint all the parameter to be positive or negative . And Rick also pointed out that would reduce the accuracy of model's prediction.     ... View more