Now let’s look again at your shoe data
If you had calculated the standard deviation (SD) of the distribution of shoe sizes and found out it was 2.0* you would know that 68.26% of males probably have shoe sizes between 7 and 11. This is 9 + 1 SD or 9 + 2. (Hint: look back at the shoe table with the normal curve in it and figure out the SD visually.)

Now you estimate how many pairs of shoes you might need for each shoe size by filling in the boxes under the curve.

Preview: In z-scores you will see how to pin down these percentages even more exactly.