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.

Since at the 95% confidence, the difference between the number of croaks per hour between southern and northern region frog is lying in the rage 7.1 to 8.1, this shows that the southern region's frogs' croak frequency is highly likely to be greater than that of northern region's frogs' croaks' frequency.

The claim supported by the interval is

Option C. The southern frogs are likely to have a greater mean number of croaks per hour than the northern frogs.

What does the interval tell obtained in the hypothesis testing?

The interval we obtain at certain confidence tells that the value of the test statistics will lie in that interval with that confidence.

How to identify what is the obtained interval indicating?

Since the test statistics was measuring the croak frequency difference

with southern - northern, and since at 95% confidence, the difference will lie in interval (7.1, 8.1), which is positive, thus the frequency of crocks for southern frogs is greater than the frequency of crocks for northern frogs.

Thus,

The claim supported by the interval is

Option C. The southern frogs are likely to have a greater mean number of croaks per hour than the northern frogs.

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