Exam score was regressed on hours studied for 20 students. With t∗=2.101 (df 18), which is a 95% confidence interval for the slope? PredictorConstantHoursCoef52.43.15SE Coef4.100.90T12.783.50P0.0000.003
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The slope is the Coef in the Hours row: b=3.15, with standard error SEb=0.90. Constant is the intercept.
T is Coef over SE: 3.15÷0.90=3.50. It tests slope =0, so it is not the t∗ for the interval.
Margin of error =t∗×SEb=2.101×0.90≈1.89.
3.15±1.89 gives (1.26,5.04). Zero is not inside, so the data show a positive slope.
Traps: the Constant row is the intercept, one SE is not the margin, and T is not t∗.