Question

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

Answer 1

Dividing the number of tires that should be installed per day which  is 400 by the number of working hours which is 8 will give us 50 tires per hour. Assuming that the same mistake will take toll on the workers such that they will have 1 tire mistakenly installed in an hour, they will have 8 erroneous tires in a day. Multiplying this by 5 to make the answer per week will give 40. Out of the 400 x 5  = 2000 tires. The answer would be 2000 - 40 which is equal to 1940. The assumption must be valid. 

Answer 2

Answer:

A. 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.