Number of antennas per an antenna module will increase in upcoming 5G millimeter wave (mmW) radio products. The usage of antenna arrays compensates the increased propagation loss of a radio signal at mmW frequencies. The worst performing antenna defines the quality level MIMO antenna module. This paper presents an analysis and a relationship between the variation of the antenna resonance frequency and the reflection coefficient. A probability density function (PDF) of the antenna reflection coefficient at the specification limit is a non-linearly scaled mirrored version of the PDF of the variation of the antenna resonance. We measured the PDF of antenna reflection coefficient from manufactured prototypes and there is a good correlation between the measured and the simulated PDFs.