On the TI-Nspire, you can plot a value on a histogram that displays as a vertical line perpendicular to the horizontal axis at a point equal to the specified value. In the third screen, press [MENU]→Analyze→Plot Value. At the prompt, type mean(correct) and press [ENTER]. (See the third screen.)
You can plot a single number or an expression that equals a number. Statistical values such as mean or standard deviation are good choices for Plot Value.
The Plot Value feature is also available with dot plots and box plots.
To remove a plotted value, move the cursor over the vertical line and press [CTRL][MENU]→Remove Plotted Value. To hide a normal curve, press [MENU]→Analyze→Hide Normal PDF.
Try hovering on the normal curve, right-clicking ([CTRL][MENU]), and choosing Shade Under Function. Shade a region under the curve by clicking the lower and upper bounds of the interval to display the corresponding probability associated with this interval.