You are conducting the following series of observational studies to determine if generally understood parameters about a local population are accurate:

A. You stand on the sidewalk next to a stop sign to observe and record the number of cyclists and drivers who stop or don't stop.

B. You inform customers at a local fast food restaurant of your study to determine the proportion of healthy food choices from the menu and then observe their choices.

C. From your car in the mall parking lot, you observe the proportion of shoppers who hold the door open for the next person who enters or exits the mall.

D. To estimate the proportion of males and females in the local community, you observe spectators at a hockey match and count and record the gender in a randomly selected area of the crowd.

E. You review the daily sign-in sheets at a local fitness center to estimate the average number of workouts per week for residents of the local community.

Which observational study should yield the most accurate results?

What situation would most warrant the method of observational study to produce accurate results?