This document discusses a case study on the normal probability distribution. It examines the weekly wages of 1000 workers which are normally distributed with a mean of Rs. 70 and standard deviation of Rs. 5. It estimates the number of workers whose weekly wages are: (i) Between Rs. 70 and Rs. 72 (155 workers) (ii) Between Rs. 69 and Rs. 72 (235 workers) (iii) More than Rs. 75 (159 workers) (iv) Less than Rs. 63 (81 workers). The document explains how to solve each case using the normal distribution and z-table. It concludes by asking students to explain the case study on normal probability distribution.