Find a normal percentile from a probability

The cut-off is about $124.67$: $95\%$ of scores lie below it and $5\%$ above it. xInv is a score, not a probability. The curve on the screen shades the area to the left of the marked point.

As a check, the standard normal value for an area of $0.95$ is about $1.64485$. Convert it to a score using the mean and standard deviation:

The cut-off is above the mean, as you would expect for the top $5\%$.

• The score is below the mean: check Area. Entering $0.05$ finds the bottom $5\%$, giving about $75.33$ for this distribution. For the top $5\%$, use $0.95$.
• The screen shows infinity: Area $=0$ gives $-\infty$, and Area $=1$ gives $\infty$. These are not errors; enter $0.95$ for this example.
• The Area box is dashed and the screen shows Argument ERROR: enter a decimal between $0$ and $1$, not a percentage such as $95$. Tap Area, press AC once to empty it, then enter $0.95$.
• The $\sigma$ box is dashed and the screen shows Argument ERROR: the standard deviation must be positive. Tap $\sigma$, press AC once, then enter $15$.

In the steps above, typing replaces the value of the box the equals key just selected. If you tap a box instead, press AC once to empty it before typing. A second AC resets every box of this type to its defaults, so check all three values if you do that.