A researcher wanted to estimate the difference between the percentages of users of two brands of drinking water who will never switch to another brand. In a sample of 600 users of Brand A taken by this researcher, 120 said that they will never switch to another brand. In another sample of 500 users of Brand B taken by the same researcher, 80 said that they will never switch to another brand.

Let p₁and p₂be the proportions of all users of Brands A and B, respectively, who will switch to another

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brand.

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(a)What is the point estimate of p₁- p₂?

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(b)Construct a 95% confidence interval for the difference between the proportions of all users of the two brands who will switch and interpret the result.

(c)Mention the value for margin of error with formula.