For an investigation of the mechanism of wound healing, a biologist chose a paired design, using the left and right hindlimbs of the salamander Notophthalmus viridescens. After amputating each limb, she made a small wound in the skin and then kept the limb for 4 hours in either a solution containing benzamil or a control solution. She theorized that the benzamil would impair the healing. The accompanying table shows the amount of healing, expressed as the area (mm2) covered with new skin after 4 hours.35
(a) Assess the effect of benzamil using a t test at α = 0.05. Let the alternative hypothesis be that the researcher's expectation is correct.
(b) Proceed as in part (a) but use a sign test.
(c) Construct a 95% confidence interval for the mean effect of benzamil.
(d) Construct a scatterplot of the data. Does the appearance of the scatterplot indicate that the pairing was effective? Explain.