Anna's students were not able to replicate the results of her published findings. in this scenario, anna has most likely committed the act of observational research.
An observational study draws from a sample of a population where the independent variable is not controlled because of ethical reasons and personal interference and sometimes constraints. The researcher therefore observes the population of choice without manipulation or interference.
A designed experiment is under controlled conditions, in which the researcher manipulates variables to determine a output and it constantly inputting things to improves the final result. Designed experiment is always under controlled environments with many things being anticipated or calculated.
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