A biologist studied the frequency of croaks for frogs from two different regions. From a random sample of 32 frogs located in the northern region, the mean number of croaks per hour was 21.3, and from a random sample of 38 frogs located in the southern region, the mean number of croaks per hour was 28.9. To estimate the difference in the mean number of croaks (southern minus northern), a 95 percent confidence interval was constructed from the samples. The interval was reported as (7.1, 8.1). Which of the following claims is supported by the interval? A. All southern frogs croak more times per hour than do all northern frogs.
B. The northern frogs are likely to have a greater mean number of croaks per hour than the southern frogs.
C. The southern frogs are likely to have a greater mean number of croaks per hour than the northern frogs.
D. All frogs in the study have about the same number of croaks per hour.
E. The northern and southern frogs have the same mean number of croaks per hour.