Theoretical framework
Heckman two stage estimation method
In the study, as some of the consumers did not buy any of the
frozen products (potatoes, peas, green beans, strawberries or
cherries), zero expenditure and zero consumption were observed in
the data. In cases where the dependent variable observation is
zero, sample selection bias can occur and the use of the least
squares method can lead to biased and inconsistent parameter
estimates. In such cases, the Heckman method is used. The aim of
this method is to obtain non-biased, consistent parameter estimates
(Harmon, 2003).