I am a beginner in learning Statistics with some knowledge of machine learning, some concepts really confused me recently.
Starting from the linear regression and OLS, I think the former is a model with parameters/coefficient and the latter is the method I used to estimate the parameters for the linear regression model. So the relationship between them is the model and estimating method.
However, I read papers using the Gravity Model to describe some phenomena or test hypotheses, some of them estimate the parameters by OLS, but the others use "models" like Poisson, negative binomial to "estimate" the parameters.
I am confused, how can I use one "model" to estimate the parameters of another?
It must be something wrong with my concepts system, and I really need someone to correct me.
In addition, I want to use econometrics methods/models to perform my research (not in the field of statistics or econometrics), is there any books with practical examples and code I can read? Since textbooks I read pay a lot of attention to prove something and lack a macro view of the whole system, I am still not able to perform actual experiments even I obtain that knowledge. Maybe books with some end-to-end examples can help.