I wonder which statistical book your Z-value table is in? The standard normal distribution diagram is calculated by statisticians in the form of calculus (which cannot be expressed by Formula 3.0 here), and then drawn, in which the horizontal axis is the z value and the vertical axis is the y value, indicating the proportion, and the total area covered by the curve is 100%. If you refer to the book Education Statistics edited by Wang Xiaoling, the first table at the end of the book is the normal distribution table: the area P you want to know refers to the area covered by vertical lines and curves from the normal distribution chart with Z=0 to a certain z value. I call it area p in the table. For example, when Z= 1, the area p in the table is 0.34 134, that is, the curve area from Z=0 to Z= 1 is 0.34134 (34.134%); If you are given a negative z value, you can also check it and take an absolute value to check it. For example, when Z=-2, the area in the table is checked by Z=2, and p is 0.47725.