P(85 < X < 115) = 0.6827shaded 68.27%lower 85 · z -1.00 · percentile 15.9upper 115 · z 1.00 · percentile 84.1
meanxz55-370-285-1100011511302145385z = -1.00115z = 1.00
drag a boundary, or click anywhere on the curve to send the nearest one there · arrow keys nudge, shift for finethe curve is drawn from mean minus 4 SD to mean plus 4 SD, so its shape never changes

One SD either side of the mean, from 85 to 115, holds 0.6827 of the curve. That is the 68 in the 68-95-99.7 rule, and it stays 0.6827 for every mean and every SD you can set.

Try to: shade about 95% between two symmetric bounds find the 90th percentile with the right tail push a boundary past z = 2 lock the z-scores, then move the mean

Normal curve area and z-score explorer · free from StatsLearn