Students Struggled With…
Solving for a sample size for a desired margin of error. Really the hardest part is doing the algebra, especially because when you square a decimal, it gets really, really small. Students tend to round which changes their final answer substantially.
Practice, practice, practice! A helpful trick when solving is to split the square root up in the numerator and denominator. Then multiply by √n to get n out of the denominator. Don’t square until the final step! This should help students to get more accurate final answers.