The body of the tables contains four or five digit numbers with values corresponding to the area represented by the shaded region, as the z-value changes. The left column of all the tables contained the first two digits of the z-value. It is the probability that a standard normal random variable, Z, is less than or equal to the z-value, between the mean and the z-value or greater than or equal to the z-value.
How to read a standard normal table pdf#
The shaded area represents the area under the PDF given in the body of the table. The key is to check the small sketch of the normal curve with a z-value indicated on the x-axis and a shaded in the area under the curve. There is not a “ standard” standard normal tableĪ quick check in a few books found three different layouts for the table. The issue is each author may present the table in one of many manners. Most statistics books, and many reliability engineering books include a standard normal table in an appendix. This means that if you can estimate the area under the PDF for a standard normal distribution, you can estimate the area under the PDF for a normal distribution with any mean or standard deviation. The standard normal has a mean of zero and standard deviation of one.
By subtracting the mean and dividing by the standard deviation for each point of in the dataset, the results have a standard normal distribution. The normal distribution has the very pleasant property that it can be normalized. There is no closed form solution for the integral of the normal distribution probability density function, it requires advanced numerical methods to estimate the area under the curve.
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