At Community Hospital, the burn center is experimenting with a new plasma compress treatment. A random sample of n₁ = 316 patients with minor burns received the plasma compress treatment. Of these patients, it was found that 259 had no visible scars after treatment. Another random sample of n₂ = 419 patients with minor burns received no plasma compress treatment. For this group, it was found that 94 had no visible scars after treatment. Let p₁ be the population proportion of all patients with minor burns receiving the plasma compress treatment who have no visible scars. Let p₂ be the population proportion of all patients with minor burns not receiving the plasma compress treatment who have no visible scars.

(a) Check Requirements Can a normal distribution be used to approximate the ₁ – ­₂ distribution? Explain.

(b) Find a 95% con­fidence interval for p₁ – p₂.

(c) Interpretation Explain the meaning of the con­fidence interval found in part (b) in the context of the problem. Does the interval contain numbers that are all positive? all negative? both positive and negative? At the 95% level of confi­dence, does treatment with plasma compresses seem to make a difference in the proportion of patients with visible scars from minor burns?