A researcher wanted to estimate the difference between the percentages of users of two tooth pastes who will never switch to another tooth paste. In a sample of 500 users of Toothpaste A taken by this researcher, 100 said that they will never switch to another toothpaste. In a sample of 400 users of Toothpaste B taken by the same researcher 68 said that they will never switch to another toothpaste.
(i) Let p1 and p2 be the populations of all users of Toothpastes A and B, respectively who will never switch to toothpaste. What is the point of p1-p2?
(ii) Construct a 98% confidence interval for the difference between the proportions of all users of the two toothpastes who will never switch
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