A trial of impact evaluation utilizing effect size statistics: Its application to the evaluation of Japan's foreign student policy

This article proposes a method of evaluating effect, impact and efficiency of treatment using the standardized mean difference (SMD) of outcomes between the treatment and the control groups. Since the SMD is commensurable (divisible and measurable by a common standard), here it is given a unit name 'effect' as an expression of the 'standardized effect'. Based on the assumption that impact is the sum total of the change brought about by the treatment in the population, this article asserts that impact can be calculated by multiplying the 'standardized effect' by the population under treatment given that the sample represents the population. Extending this logic, efficiency can be calculated by dividing the impact by the total input of the treatment expressed in a monetary value. An example of the application of this approach to the evaluation of Japan's Foreign Student Policy toward Thailand is introduced and its merits and limitations are discussed.