A researcher conducts an independent-measures research and obtains t = 2.070 with df = 28. QUESTION: Compute r2 to measure the percentage of variance accounted for by the treatment effect? Solution Critical value = t(.025; 28 d.f.) = ±2.048. The critical value has a positive and negative sign since it is a two tailed test. Since t=2.07 > critical value = 2.048, we reject Ho. There is a significant difference between the two treatment conditions..