The median is the number that is at the center of a dataset when the dataset is arranged either in ascending or descending order.
The scores arranged in ascending order : 3, 4, 7, 8, 9
Median = 7
Quartile divides the dataset into four equal parts.
Lower quartile = 1/4 x ( n + 1)
Upper quartile = 3/4 x ( n + 1)
The number of customers arranged in ascending order: 30, 60, 70, 70, 80, 80, 90, 100, 120, 120, 150
Lower quartile of customers = 1/4 x ( 11 + 1) = 3 = 70
Upper quartile of customers = 3/4 x ( 11 + 1) = 9 = 120
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