24. Melinda conducted an experiment regarding the effectiveness of two graphic design training courses, Image-nation and Perfect Pics. She randomly selected 20 people from her marketing team and assigned 10 team members to each training course. To determine the effectiveness of Image-nation and Perfect Pics, Melinda assigned the same task to all participants at the beginning and at the end of each program. She stated that a training course is effective if there is a decrease in time required to complete a graphics task. At the beginning of each course, Melinda found the average time to complete a task for Image-nation participants to be 60 minutes and the average time to complete a task for Perfect Pics participants to be 70 minutes. At the end of each training course, Melinda found the time taken to complete a task for Image-nation participants to be 50 minutes and the average time to complete a task for Perfect Pic participants to be 55 minutes.

Which statement should be included in Melinda’s report of the experiment's results?

A. Image-nation is the only course that resulted in a decreased average time to complete a task; therefore, Image-nation is the more effective course.
B. Perfect Pics is the only course that resulted in a decreased average time to complete a task; therefore, Perfect Pics is the more effective course.
C. The Image-nation course and the Perfect Pics course are both effective because the average time to complete a task decreased for each course; however, Perfect Pics is the more effective course because it yielded a greater decrease in the average time to complete a task.
D. The Image-nation and Perfect Pics courses are both effective because the average time to complete a task decreased for each program; however, Image-nation is the more effective program because it yielded a greater decrease in the average time to complete a task.