## Elementary Statistics (12th Edition)

The mean can be counted by summing all the data and dividing it by the number of data: Jefferson Valley: $\frac{6.5+6.6+6.7+6.8+7.1+7.3+7.4+7.7+7.7+7.7}{10}=7.15$, Residence: $\frac{4.2+5.4+5.8+6.2+6.7+7.7+7.7+8.5+9.3+10}{10}=7.15$. The median is the average of the 1 or 2 (here 2) middle data: Jefferson Valley:(7.1+7.3)/2=7.2, for African American drivers:(6.7+7.7)/2=7.2. The African American drivers appear to speed more because their mean is more. There is no difference between the measures of centres because they are equal.