The quality assurance department of a chair factory samples daily production to test for the strength of the chairs being produced. what is the population they are testing for quality? a. one days production b. one weeks production c. all the chairs with the same style

The only way to assure quality of the chairs is to test all the chairs produced.
One day or one week just covers a small fraction of the all the chairs produced and they may have the quality necessary but that doesn't mean all the chairs have that quality.
The correct option whould be  all the chairs produced but since you don't have that one, choose option c.