A holistic therapist was interested in determining whether aromatherapy affected patients' mean anxiety scores. The therapist hypothesized that there would be a difference between patients' anxiety scores before and after treatment with aromatherapy. He used a single sample of 8 participants. The mean of the difference scores was 6.0 (M_D = 6). The SS for the differences scores was 168 (SS_D = 168). The researcher set the alpha level at .05 ( = .05). Find the t-critical value.