Select an appropriate data collection method

Detailed Explanation: Select an appropriate data collection method

Start by asking three questions:

1. Who is the population?
   The population is the whole group you want to learn about.

2. What information is needed?
   Is it a count, an opinion, a behavior, or a measurement?

3. Will anything be changed?
   If you change something to see its effect, you need an experiment.

Use these clues:

• Census: Collect data from every member of the population.
• Sample survey: Ask some members questions to estimate information about the whole population.
• Observational study: Record what people do or what conditions are like without changing anything.
• Experiment: Assign different treatments or conditions and measure the results.

Worked example

A teacher asks:

“Does listening to quiet music while studying affect Grade 7 students’ quiz scores?”

Step 1: Identify the population

The population is all Grade 7 students the teacher wants to understand.

The teacher probably does not need to test every Grade 7 student. Testing everyone would take a lot of time.

Step 2: Identify the variables

The teacher will record:

• Study condition: quiet music or no music
• Quiz score: the number of questions each student answers correctly

The quiz score is the evidence that will help answer the question.

Step 3: Decide whether something will be changed

The teacher plans to give some students quiet music and other students no music while they study. Because the teacher is assigning conditions, this is an experiment.

It is not an observational study because the teacher is not merely watching students choose whether to listen to music.

Step 4: Choose students fairly

The teacher could randomly select students from the Grade 7 student list. Random selection gives students a fair chance of being included and helps the group represent the population.

Then the teacher could randomly assign the selected students to the two groups:

• Group 1: studies with quiet music
• Group 2: studies without music

Random assignment helps make the groups similar before the study begins.

Step 5: Check for possible problems

The teacher should consider bias:

• Undercoverage: If the teacher only selects students from one class, other Grade 7 students are left out.
• Nonresponse: Some selected students may not participate.
• Unfair conditions: One group might get more study time or an easier quiz.

The teacher should use the same study time and the same quiz for both groups.

Conclusion

The appropriate method is an experiment because the question asks whether one condition, listening to music, affects another variable, quiz scores. Random selection helps the results represent Grade 7 students, and random assignment makes the comparison fair.