Question

A scientist who is researching marshes observes that marsh grass, Spartina bakeri, grows to different heights at different locations in the marsh. If the scientist wants to find the reason for this difference, what is the correct first step? Conduct an experiment and change only one variable at a time. Determine which technology would assist most in answering the question. Form a research question based on knowledge of the marsh. Establish a control group for comparison.

Answer 1

I belive "form a research question based on knowledge of the marsh," in other words, your hypothesis which is the 1st step in the scientific method after observation (which your scientist has already done)

Answer 2

The correct first step would be to conduct an experiment and change only one variable at a time.

There are generally two types of variables in all the valid research, that is, independent and dependent variables. These variables permit a researcher to find the precise association among the variables.  

Thus, in the given study, if the scientists are aiming to determine the cause of length distinction in the marsh grass, then he has to perform an experiment with the application of independent and dependent variables.