An experiment was conducted to test the effects of alcohol.The errors were recorded in a test of visual and motor skills for a treatment group of people who drank ethanol and another group given a placebo.The results are shown in the accompanying table.Use a 0.05 significance level to test the claim that the treatment (alcohol) causes an increase in visual and motor skills errors?

What is the critical value? (Round your answer to 3 decimal places.)

Alcohol Placebo

Mean 3.20 1.71

Standard Deviation 2.20 0.72

Size 20 22