ased on the information provided, a suitable statistical test to determine if there's a large difference in concentration levels between the coffee and placebo groups would be the t-test for independent samples.

To execute this test, we need to first collect data for both groups, namely the coffee group and the placebo group. Then, we need to calculate the mean and standard deviation for each group. Finally, we can use a t-test to determine if there is a significant difference in mean concentration levels between the two groups.

Once the t-test has been applied to the data, we can conclude if there is a large difference in concentration levels between the coffee and placebo groups. The exact response will depend on the specific data obtained and the outcome of the statistical test.
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