Performance in primary education can be measured in terms of different variables, like enrolment rate, attendance rate, or levels of learning achievement of students. Thus, for an analysis of the comparative performance of units, like country, state, or district, we need an aggregate measure or an index developed from these variables. In constructing such an index, we find a suitable average of the variables used with appropriate weights assigned to each of them. The method of principal component analysis (PCA) helps in determining these weights endogenously. This case study describes my research on the construction of an index of performance for primary education in India, called the Educational Outcome Index (EOI). I used data on 10 variables and applied the method of PCA for the construction of the EOI. In my research project, I calculated the EOI for 161 districts across six selected states of India. Subsequently, I classified the districts into three groups of performance--good, average, and poor, on the basis of their EOI values. The classification indicated considerable intrastate variations in the outcome of primary education in India. From this case study, the reader will learn about the method of PCA, especially the conditions under which the method could be used and the different steps in its application. Taking insights from this case study, the readers would be able to apply PCA for index construction in their own field of research, if required. [This content is provided in the format of an e-book.]