A bicycle factory installs about 400 tires per day. Tires are installed Monday through Friday for 8 hours per day. The manager of the factory estimates the number of properly installed tires per week using the process below.

Question

In the first hour of work on Monday, 49 out of 50 tires were properly installed.

So, there were about 8(49) = 392 properly installed tires on Monday.

Considering 5 working days per week, 5(392) = 1,960 is the number of tires properly installed in one week.

Which best explains the validity of the results?
The results are likely invalid because it is unlikely that the tires installed in one hour on Monday will represent the entire population of tires.
The results are likely invalid because the entire population during one week was not part of the sample.
The results are likely valid because a large number of tires produced during the week were part of the sample.
The results are likely valid because each tire sampled was part of the population of tires that week.

Answer 1

The best explanation for the validity of the results is:

The results are likely invalid because it is unlikely that the tires installed in one hour on Monday will represent the entire population of tires.

This is because the sample size (49 out of 50 tires installed in the first hour of Monday) is not sufficiently large or random to accurately reflect the quality of all tires installed throughout the entire week. Factors such as variability in worker performance, maintenance of machinery, or changes in tire quality could affect the installation process on different days or at different times, leading to different rates of properly installed tires. Therefore, conclusions drawn solely from one hour's performance may not be representative of the entire week's production.