The importance of attendance

One day I'm going to sit down and crunch the numbers on this, to get absolute proof. Regardless of the flaws in my data collection, I feel confident in saying that students who miss a lot of class end up with lower grades. And that's before the late penalty is added in.

For evidence I offer the following chart of grades and absences from two sections of the same undergraduate literature class. Notice the correlations after 9 absences--missing more than 3 weeks of class.

Average	Absences
0.8975	0
0.9026	1
0.8749	2
0.927	2
0.8694	2
0.7117	2
0.887	3
0.8669	3
0.8654	3
0.8478	3
0.9609	3
0.8712	3
0.9296	3
0.9311	3
0.8658	3
0.8684	3
0.815	3
0.6684	3
0.8893	3
0.8951	3
0.8571	3
0.8492	4
0.8423	4
0.9549	4
0.9195	4
0.8682	4
0.8893	4
0.9124	4
0.8364	4
0.8088	4
0.9016	4
0.9133	4
0.921	4
0.9254	4
0.8686	5
0.8512	5
0.8427	5
0.8238	5
0.8084	5
0.7495	5
0.8531	6
0.5819	7
0.8561	7
0.8788	7
0.7998	7
0.884	8
0.8017	9
0.8985	9
0.7992	10
0.7742	12
0.7273	13
0.7956	14
0.7326	14
0.6206	16
0.7638	16
0.7191	19
0.4008	21