An alternative to a controlled experiment would be a (n). a ... quantitative study. b ... correlation study. c ... field study. d ... a library research paper.

Controlled experiment is an experiment done under controlled conditions in which only one variable at a time is changed in order to isolate the results. An alternative to a controlled experiment would be a correlation study. A correlation study is a research method in which two variables are compared (what are the similarities and the difference between them). So, correlation study is a type of controlled experiment in which ove variable is changed and the dependence with another variable is analyzed.