A customer service center keeps track of the number of complaints received each day about one of their new product. The number of complaints received over the last 11 day perload are 19, 18, 22, 21, 17, 18, 22, 19, 16, 23, and 25. The IQR for this sample of data is ___
a. 9
b. 4
c. 25
d. 22
3. 18