To calculate the mean absolute deviation (MAD), follow these steps: First, find the mean of the data set by adding all the values and dividing by the number of values. In this case, the mean of the chocolate bars sold is (8 + 8 + 8 + 6 + 7) / 5 = 7.4. Next, calculate the absolute difference between each data point and the mean. For each student: the absolute differences are |8 - 7.4| = 0.6, |8 - 7.4| = 0.6, |8 - 7.4| = 0.6, |6 - 7.4| = 1.4, and |7 - 7.4| = 0.4. Then, find the average of these absolute differences: (0.6 + 0.6 + 0.6 + 1.4 + 0.4) / 5 = 3.6 / 5 = 0.72. Finally, round this value to the nearest tenth, resulting in a mean absolute deviation of 0.7.