ABSTRACT
There are two principal applications of the normal distribution to engineering and reliability. Many natural occurrences such as the heights or weights of a group of people, the sizes of components produced by a particular machine and the life length of certain components approximate to a normal distribution. The total area under the standardised normal curve is unity and since the curve is symmetrical, it follows that the total area to the left of the 0 ordinate is 0.5000. To test the normality of a distribution, the upper class boundary/percentage cumulative frequency values are plotted on normal probability paper. The calculated values of the mean and standard deviation of the distribution are 45.9 and 19.4 respectively, showing that errors are introduced if the graphical method of determining these values is used for data that is not normally distributed.
