If the weight of wrestlers on the team varies by 74 pounds, the best way to measure this would be the range.
The range indicates how much difference there is between the maximum and the minimum values, thus making it perfectly suited for finding the variance between the weights of wrestlers.
The most popular M&M color being green could be best verified by the mode.
The mode of a set is the most commonly occurring number in that set, so this would be the best way to find the most commonly occurring type of candy.
If the mean price for a download is $1.96, this could be verified by finding the mean.
The mean is the average of a data set, so this could verify that this price was the best indication of the average of the mp3 downloads.
Finally, if half the students in PE are 15 or older, this could be determined by the median.
The median is the middlemost value in a data set, so it would help you in this instance because it would allow you to see where the halfway point was in the ages of PE participants.
Hope this helps!
