SOUTHERN WORCESTER COUNTY — The Citizen Chronicle recently published MCAS data from the schools in its coverage area. Within that posting, we included a bar graph that showed scores throughout the coverage area as well as a series of bar graphs that compared each individual district’s test scores over the last two academic years.
It was within those individual charts that The Citizen Chronicle unwittingly made an error. As pointed out by two local mathematics teachers, there was an error in the scale marks being used. The data shown within the charts was accurate, but one of the charts featured a maximum output on the graph of 90, while others had a maximum output of 100, and some others topped out at 120. As a result, a comparison of the various charts may have unintentionally led readers to see lesser or greater differences because of the relative height of the bar graphs. The Citizen Chronicle regrets this error, which we first learned upon a math teacher pointing out the misleading mistake.
Another Shepherd Hill Regional High School mathematics teacher spotted the same error and asked one of their AP Statistics students to improve upon the bar graphs The Citizen Chronicle had poorly constructed. The Citizen Chronicle thanks the teachers and the student for the diligence and keen eyes, as well as the effort to modify and correct our mistake.
“The first thing that you learn about graphs in a Statistics class is that data being compared must be done so in a way that is equal and truthfully representative. A major component of that principle is graphing data on the same scale: using the same maximum and minimum value, and counting by the same interval. Additionally, axes need to be labeled — otherwise, the data displayed is nothing more than meaningless numbers,” Shepherd Hill senior Cameron Cushing explained. “Graphs included in an earlier article violated both of these principles, showing a misrepresentative snapshot of local school areas’ performance on the MCAS standardized test. To better represent the Department of Elementary and Secondary Education’s data, new graphs are included that display scores for each High School in a single subject area.”