Grid operators are required to ensure the secure and stable operation of the power grid. With increasing penetration of distributed generation in the grid, especially at lower voltage levels, this task is becoming more complex for system operators, leading to the need of an improvement in their coordination efforts. To tackle this issue, different methodologies to present the flexibility provision within a distribution grid in an aggregated manner have been developed. This paper focuses on validating the results provided by such aggregation algorithms. A random sampling approach is used to validate the obtained flexibility range of a distribution grid obtained through a previously developed linear optimal power flow algorithm. By means of a ‘beta’ instead of a ‘uniform’ distribution for the selection of the random variables, the flexibility ranges become comparable and a validation of the results is applicable. A case study is performed using the CIGRE test-bench grid. Results show that optimization-based aggregation algorithms can provide accurate results, while respecting grid constraints and showing a convex behavior.