An experimenter is interested in whether reading before going to bed will influence people's sleep quality. The experimenter randomly assigns subjects to two groups. The data consist of subjects' ratings of how well they slept, with higher ratings indicating better sleep:

Control group:3, 4, 6, 5, 2, 4

Experimental group:5, 9, 6, 8, 7, 6, 4, 6

What is the critical value from the t table assuming alpha = 0.05?