Answer :
Using confidence interval concepts, it is found that the reasonable estimate for the proportion of all American adults who believe that regular exercise is important is of 0.753.
What is a confidence interval?
It is the range in which a parameter is expected to be given a confidence level, has format (a,b), and the point estimate of the parameter is the mean between a and b.
In this problem, the interval is [0.726, 0.780], hence, the estimate is of:
(0.726 + 0.78)/2 = 0.753
You can learn more about confidence interval concepts at https://brainly.com/question/25779324