Is it true or false that a scientific experiment can be conducted only in a laboratory?

No. Experiments can be done anywhere. Laboratories are indeed handy as they have equipments and surroundings needed for most of the experiments, but you cannot limit experiments to the labs.

The answer to this actually depends on how you define the Word laboratory.

If by a laboratory, you mean 'a special room set aside to conduct scientific experiments' then the answer is no. Experiments can be conducted in the field (in other Words, outside the lab or even outdoors) in what is known as field research.

However, if you define a laboratory as 'a place in which experiments are conducted' (as in, "The whole world is my laboratory") then the answer is yes. By this definition, wherever you happen to be conducting your experiment - the classroom, the beach, the International Space Station, or even inside your own head - would be considered your lab space.

The way you've phrased the question, however, makes me believe that you intended the Word laboratory to have the first definition, i.e. a lab room. By that definition, the answer you're looking for is false, for the reasons outlined above.