Question

experiments or observational studies in which only one variable is manipulated are described as
observ
dependent
cont ed
independent

Explanation:

In experimental design, a controlled experiment (or study) is one where only one variable (the independent variable) is manipulated, while other variables are controlled to observe the effect on the dependent variable. The options "observed" is about noting, "dependent" is the variable being measured, "independent" is the manipulated variable, but the study type with one manipulated variable is "controlled".

Answer:

controlled (from the green - colored option with "controlled" text)