Ideally there would be 30 or over students randomly chosen.
The class probably has less than 30 students to begin with.
And the bias and friction for students to set up an account and review makes these results spurious to begin with.
Still, three hour lectures ? I don't need my University's School of Education to tell me that's not an effective way to teach humans anything.
We know in a safety critical environment, where giving something your full attention is vital to the survival of yourself and others you care about, human watch keepers are not effective for the 4-8 hours they are often given this task, even though they know that becoming ineffective will get somebody killed.
For lab work, where setting up and shutting down are time-consuming, and a mix of activities may help improve focus, a double (2 hour slot) might be reasonable anyway but if you're planning three hours of standing at the front talking, your students are not going to benefit anything close to how much they would from three separate one hour lectures.
