Definition: - The standard normal distribution table gives the probability of a value being between a particular value of z and the mean. The whole number and tenths- palace appear in the first column of the table. Across the top of the table are the values of the hundredths – place portion of the z score.
To read the z score table, we always start from z=0, which represents the mean of standard normal distribution table. Standard normal curve is like a bell shape and it is symmetric figure, which means area on the each side of the mean are equally distributed and equal to 0.5. Although the values of z on the left side of the mean are negative, the area under the curve is always positive for both positive z score and negative z score because z table represent the area under the curve and area cannot give a negative value.
Example: - Find the area of between z=0 and 1.06.
Solution: - Find 1.0 (the portion of this z score from the z table) from the first column. For this z score, the hundredths- place value is 6, so find 0.06 from the top of the table.
Since 1.06= 1.0+0.06.
Then take the intersection value of 1.0 and 0.06 which is 0.3554.
Another example: - Find the area between z= 0 and 2.72.
Solution: - From the z table area under z=0 and 2.72 is 0.4967