Simplify the following text for a Grade 9 native English-speaking person.
Original: Results from a word memory test showed that people with a Body mass index ( BMI ) of 20 ( considered to be a healthy level ) remembered an average of nine out of 16 words .
Simplified: Results from a word memory test showed that people with a BMI of 20 ( considered to be a healthy level ) remembered an average of 9 out of 16 words .