In a controlled setting. It has high internal validity (reduced extraneous variables. True. Researchers manipulate IV. Less demand characteristics. Can be repeated.
2) Decide how you could operationalise both of the variables, if it hasn't already been done. (To operationalise the IV, decide on which 2 there are. For the DV, you need to decide exactly how you're going to measure whatever it is you're measuring)
3)Explain how you think the independent variable will affect the dependent variable. Like a jigsaw.
Fit somewhere in between structured and unstructured. They are a predetermined list of questions to ask, however the interviewer may ask more questions if they feel it is necessary.
When the researcher takes advantage of a pre existing IV that has naturally occurred. High internal validity and provide opportunity for research, however this is rare.
Natural and quasi experiments cannot be classified as these experiments because they involve the manipulation of the independent variable and groups aren't randomly selected.