I really need help with these step by step

Which of the following is the true for f(x) = 5cos

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 .

Solve this problem! extra ! 3025/5.5 = a/90.75