In a study, both the researchers and the participants are unaware of the group assignments. a. controlb. double-blindc. pilotd. randomly assigned

B. double-blind

Explanation:

A double-blind study is one where neither the patients nor the experimenters knows who will be undergoing a specific treatment. The above method is used to eliminate bias in the outcomes of study.

These studies are especially helpful because of demand features or placebo effect to avoid bias.

For example, the researchers interacting with the participants would not know who was receiving the actual drug and who was receiving a placebo in a double-blind study.

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i only have part a but here is the first one: - lewis and clark are born

- lewis marries sacajawea and clark is jealous  

- clark drowns lewis and then goes to jail