Frequently data must be treated as a sample, although at first sight they appear to be a complete enumeration.A proprietor of a parking lot finds that business is poor on Sunday mornings. After 26 Sundays in operation, his average receipts per Sunday morning are exactly $10. The standard error of this figure, computed from week-to-week variations, is $1.2. The attendant costs $7 each Sunday. The proprietor is willing to keep the lot open at this time if his expected future profit is $5 per Sunday morning. What is the confidence probability that the long-term profit rate will be at least $5? What assumption must be made in order to answer this question?