A psychiatrist hires you to study whether her clients self-disclosed more while sitting in an easy chair or lying down on a couch. All clients had previously agreed to allow the sessions to be videotaped for research purposes. You randomly assigned 10 clients to each condition. The third session for each client was videotaped and an independent observer counted the clients' disclosures. You reported that "clients made more disclosures when sitting in easy chairs (M = 18.20) than when lying down on a couch (M = 14.31), t(18) = 2.84, p < .05, two-tailed."

Can you explain these results to me? I understand the t test for a single sample but know nothing about the t test for independent means.