This paper studies the validity of the standard method in IEC 61400-21 for assessing the flicker emission from multiple wind turbines. The standard method is based on testing a single wind turbine and then using the results of this test to assess the flicker emission from a number of wind turbines. This study is based on the data from two wind farms, one with fixed-speed wind turbines and one with variable-speed wind turbines. The data are: a type test at the terminals of a wind turbine, and measurements at the connection of a collection line to the substation. The type test data are used to assess the flicker emission at the collection line; this assessment is then compared to the actual measurements in order to study the accuracy of the estimation. It was observed in both wind farms, that the assessment based on the standard method is statistically conservative compared to the measurements. The reason for this is the statistical characteristics of flicker emission.