I did an experiment about synthesis of aspirin and I can't answer to these questions..?

Question

if your percentage yield varies from 100% explain what might have effected your yield?

If you percentage equals to 100% explain why this may or may not be a correct value?

THE ASPRIN I WEIGHTED IS 1 GRAM AND IT ASKED THE THEORETICAL YIELD OF ASPIRIN AND PERCENTAGE YIELD OF ASPIRIN

Answer 1

I have answered your (other) question on THE THEORETICAL YIELD OF ASPIRIN AND PERCENTAGE YIELD OF ASPIRIN.
Now, the percentage yield would never be100%. The reasons are:
1 Incomplete forward reaction. Have you studied backward reaction and chemical equilibrium?
2. incomplete separation/ extraction of the product.
3. etc. (Hay, I do not know how you performed your test, do I?)