Medical: Plasma Compress At Community Hospital, the burn center is experimenting with a new plasma compress treatment. A random sample of n1 5 316 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 5 419 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 pˆ pˆ 1 2 2 distribution?

Explain.

(b) Find a 95% confidence interval for p1 2p2.

(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?

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