Let's analyze the question and provide answers.

(a) Which unit(s) could be used for the unit of measurement?

The task is to measure time. Therefore:

• Seconds and Minutes are valid units for time measurement.
• Pounds, grams, and hours are not appropriate because:
  • Pounds and grams measure weight.
  • Hours are too large for such a short event.

Correct answers: Seconds, Minutes.

(b) Which procedure would be the best way to find the average time?

To calculate an average that accurately represents the population, the sample needs to be large and random. Here’s why:

1. Measure the times of 4 volunteers: This is a small sample and might not be representative.
2. Ask for 40 volunteers to state their own times: This depends on self-reported times, which can introduce inaccuracies.
3. Randomly pick 4 students and have them state their times: This is random but still a very small sample and relies on self-reporting.
4. Randomly pick 40 students and measure their times: This is the most reliable option because it’s random and uses a larger sample size, ensuring a better average representation.

Correct answer: Randomly pick 40 students to run a lap around the track and measure their times.

Let me know if you need more details or have questions!

Related Questions:

1. What is the importance of randomness in selecting a sample?
2. How does increasing sample size improve the accuracy of the average?
3. Why is self-reported data often less reliable than direct measurement?
4. How can you convert seconds to minutes for reporting averages?
5. What other factors could affect the average running time (e.g., weather)?

Tip: Random sampling ensures that every individual in the population has an equal chance of being selected, reducing bias and improving the validity of the results.