The scientific method uses observation and which other process to answer questions?

As a small change in a person's dna can cause a genetic disorder

What pattern of migration do whales follow?

Aresearcher created three groups based on participants bmi: normal weight, overweight and obese. the hypothesis being tested is that the three groups differ in the mean number of artificially sweetened drinks consumed weekly. which statistical test might the researcher use, assuming a reasonably normal distribution of values.