Inferences & Claims From Statistics Practice Test

A school surveyed 120 students who voluntarily visited the library last week and recorded their average nightly sleep and their math test score (out of 100) from the same week. The results showed a positive association: students reporting more sleep tended to have higher scores. The counselor claims, “If any student sleeps 9 hours per night, their math score will increase.” Which conclusion is most appropriate based on this observational survey?

A researcher analyzed data from 15 countries and found that countries with higher average income tended to have longer life expectancy. The researcher claims, “Raising a country’s income will increase life expectancy.” Which statement is most justified?