A fitness program is evaluated by measuring the number of push-ups completed by $12$ participants before and after a $6$-week training. The results are:

Construct the $95\%$ confidence interval for the mean difference in push-up counts. What does the interval suggest about the program's effectiveness?

• A. ; Since the interval is positive, the program was highly effective.
• B. ; Since the interval contains 0, there is no significant evidence of improvement.
• C. ; Since the interval is entirely positive, the program significantly improved push-up performance.
• D. ; Since the interval is entirely negative, the program decreased performance.

Answer: (C)