Tristan records the number of customers who visit the store each hour on a Saturday. His data representing the first seven hours are 15, 23, 12, 28, 20, 18, and 23. How many customers visited the store during the eighth hour if the median number of customers per hour did not change?

Sort the first seven counts: 12, 15, 18, 20, 23, 23, 28. The median is 20, so the eighth count must make the average of the 4th and 5th values in the sorted list equal 20. If the eighth count is 20, those middle values are both 20, so the median stays 20. The correct choice is 20 customers.

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