Sample Design to Analyze the Production Costs from Ecological and Conventional Agriculture

In order to determine a representative sample for analyzing the differences between costs’ production for ecological and conventional agriculture for vegetal sector the simple random sampling method was considered, for a relative error limit of 6% at a confidence level of 95%. The sample was established by using the formula proposed by Merce (Merce et al., 2010) and was obtained a number of 200 producers. For better results, the structure of the sample respects structure of the entire studied population regarding the geographical distribution (on development regions) and the systems of agriculture used. It was decided to increase the number of respondents included into sample to 226, because of the risk of invalidation of some applied questionnaires as results of the some errors (as are human errors in the process of recording the answers, inconsistent answers and so on) which disqualify them for further analysis and, implicit, the possibility of decreasing the number of accepted respondents below the representative size of the sample.