Been to the movies? An opinion poll calls $2000$ randomly chosen residential telephone numbers, then asks to speak with an adult member of the household. The interviewer asks, “How many movies have you watched in a movie theater in the past $12$ months?” In all, $1131$ people respond.

(a) Identify a potential source of bias related to the question being asked. Suggest a change that would help fix this problem.

(b) Identify a potential source of bias in this survey that is not related to question wording. Suggest a change that would help fix this problem.

Sample size, $n=200$

Number of people who responded $=1131$

Researchers used the replies to calculate the average number of movies adults saw in a movie theatre in the previous $12$ months.

The random assignment method assigns subjects to treatments based on chance. Before the treatments are applied, random assignment establishes treatment groups that are comparable (except for chance variance). In experiments, randomization and comparison combined prevent bias or systematic favoritism.

A poll of public opinion dials $2000$ random private phone numbers and asks to speak with a grown-up member of the family unit. "How many films have you seen in a cinema in the preceding year?" the questioner inquires. Every single one of the $1131$ people reacts. The answer bias is a likely scenario because if people watch movies frequently, they would forget the number of times they have watched movies and will say the first number that comes to mind. As a result, reaction bias is a possibility. By lowering the time duration from $12$ to $3$ months, the response bias might be eliminated.

The participants were called by residential landline, however the young generations use cell phones, and it is possible that the young generation likes to attend movies in cinemas. As a result, there is a selection bias, which might be mitigated by include people who own cellphones.