The following list contains the number of hours that a sample of 13 middle-school students spent watching television last week.
\[
9,6,18,17,13,14,4,20,13,13,9,8,11
\]
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Find the median number of hours for that sample.
hours

Step 1 ：Given the list of hours that a sample of 13 middle-school students spent watching television last week: \[9,6,18,17,13,14,4,20,13,13,9,8,11\]

Step 2 ：First, we need to sort the list in ascending order: \[4, 6, 8, 9, 9, 11, 13, 13, 13, 14, 17, 18, 20\]

Step 3 ：The median is the middle number in a sorted list. If there is an even number of observations, the median will be the average of the two middle numbers. In this case, we have 13 numbers, so the median will be the 7th number in the sorted list.

Step 4 ：From the sorted list, we can see that the 7th number is 13.

Step 5 ：Thus, the median number of hours that the sample of 13 middle-school students spent watching television last week is \(\boxed{13}\).