Which quanity container is better buy

15 points ! ~ see if you know the answer to both you!

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?