Aresearcher conducting a study testing the effects of caffeine on attention is concerned that both her expectations and subjects expectations will effect the findings of this study. so neither the researcher nor the subjects knew who was in the control and experimental groups. what technique was being used in this study?

The technique use in this study is referred to as a double blind

Explanation:

A double blind study is the one that both participants and experimenters or researchers are not made aware who is given a certain treatment.

In double blind researchers will not know if what they are receiving is part of the test itself as they interact with participants or they are receiving a placebo.

This process is useful to eliminate and avoid bias results.

For example, in the above text the effect of caffein on attention is being tested so the researchers will not know whether the drink given to them is actual for the test or just the placebo , they don't know who is in control of the experiment.