Understanding Conditional Probability (Math is Fun)

The small difference in the words implies a difference in the denominator in the calculation, while the numerator stays the same.

Suppose you in fact have $20$ friends of whom $14$ like Chocolate, and of these $7$ like Chocolate and Strawberry.

• The proportion of all your friends who like both is $\dfrac{7}{20}=35\%$
• The proportion of your Chocolate-liking friends who also like Strawberry is $\dfrac{7}{14}=50\%$

This second calculation is equivalent to $\frac{7/20}{14/20} = \frac{35\%}{70\%}$, and you would get the same percentage result if you in fact have $100$ or $2000$ friends