One hundred forty-four of the 180 seventh-grade students attended the school dance last Saturday night. What percentage of seventh-grade students did NOT attend the dance?

The median of a data set is the measure of center that is found by adding the data values and dividing the total by the number of data values that is the value that occurs with the greatest frequency that is the value midway between the maximum and minimum values in the original data set that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude