This chapter analyzes the average wind speed data observed in seven cities located in coastal and inland areas in Japan by assuming the one-way effect model with time-dependent errors and correlated groups. The purpose is to assess the existence of area effects. To this end, both the
statistic designed for correlated groups and the
statistic designed for independent groups are applied. The results highlight the greater accuracy of the former test which appropriately takes into account the correlation structure among the series.