In a study of 250 adults, the average heart rate was 70 beats per minute. Assume the population of heart rates is known to be approximately normal, with a standard deviation of 12 beats per minute. What does a margin of error of 2 for the 98% confidence interval of the average beats per minute mean?
A, There is a 1% chance that the population mean is less than 70 beats per minute.
B, There is a 1% chance that the population mean is more than 70 beats per minute.
C, There is a 99% chance that the population mean is between 58 and 82 beats per minute.
D, There is a 99% chance that the population mean is between 68 and 72 beats per minute.