S.No. Categories of farms Total number of commercial dairy farms in Tehran Number of farms selected by probability proportionate sampling technique
1 Farms that had 100 cattle 31 13
2 Farms that had 101-250 cattle 41 17
3 Farms that had 251-500 cattle 28 11
4 Farms that had more than 500 cattle 80 33
Table 1: The total number of different categories of Holstein farms in Tehran Province, and the selected number of farms in the respective categories, on the basis of Probability Proportionate Sampling Technique.