As the CEO of CELL, you want to understand the demand of yourlaptop YPS in the next year, so that you can arrange production plan ahead of time.

You hired one economic consulting rm to help you collect the price and quantity data, together with other variables necessary to estimate the demand. You paid them half a million USD as consulting fee. After 3 months, the consulting rm give you the data and estimated demand function X(P;M;Z), where P is the set of prices, M is income, and Z is product attributes for YPS laptop and other relevant products.

(b) How do you know that the data you received from the consulting rm is actually from consumer optimal choice (or in another words, how do you know the firm did not make up the data), and that the estimate of demand function is valid? Design one practical procedure to check the data quality. List the procedure step by step.