Assuming a null hypothesis of no relationship between exposure to pollution and risk of developing tumors, which of the following values is closest to the expected number of fish with tumors in the polluted lake?

Humans aren’t the only animals that get cancer; other organisms get tumors, as well, and their risk may be influenced by environmental factors. An ecologist decides to study whether pollution in lakes causes cancer, so he collects 100 fish from each of two lakes, one known to be polluted and the other known to be pristine. He then dissects them and determines if they have tumors in their tissues or not. His data is shown below.
​
​ Polluted Pristine
Tumors present 26 15
No tumors 74 85

Assuming a null hypothesis of no relationship between exposure to pollution and risk of developing tumors, which of the following values is closest to the expected number of fish with tumors in the polluted lake?
Group of answer choices

15.5

20.5

25.5

30.5

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