At the two extremes value of zoo right extreme and z-ooleft extreme Area of one-half of the area is 0. And, because we know that z-scores are really just standard deviations, this means that it is very unlikely (probability of \(5\%\)) to get a score that is almost two standard deviations away from the mean (\(-1.96\) below the mean or 1.96 above the mean). z1.65 Fig-1 Fig-2 Fig-3 To obtain the value for a given percentage, you have to refer to the Area Under Normal Distribution Table Fig-3 The area under the normal curve represents total probability. Thus, there is a 5% chance of randomly getting a value more extreme than \(z = -1.96\) or \(z = 1.96\) (this particular value and region will become incredibly important later). Math > AP®/College Statistics > Exploring one-variable quantitative data: Percentiles, z-scores, and the normal distribution > Normal distribution. Normal distribution: Area above or below a point. We can also find the total probabilities of a score being in the two shaded regions by simply adding the areas together to get 0.0500. Standard normal table for proportion above. What did we just learn? That the shaded areas for the same z-score (negative or positive) are the same p-value, the same probability. \( \newcommand\), that is the shaded area on the left side.