The half_fixed model is likely the better choice, as it is simpler and the test does not show a significant difference between the two models.

Estimate the OLS model: ols_model <- lm(Price ~ Amount + control, data = df)

Estimate the fixed effects model: fixed_model <- plm(Price ~ Amount + control, data = df, model = "within")

Perform the Hausman test: phtest(fixed_model, ols_model)