Proportion of people who are not satisfied with the service offered = 0.4
Let, p = proportion of people who are satisfied with the service offered
p = 1-0.4 =0.6
Let, x = number of customers who are satisfied
Sample size, n=400
The probability that between 156 and 240 customers will be satisfied with the service offered by the store is equal to
"P(156\u2264x\u2264240) = P(\\frac{156- (400)(0.6)}{\\sqrt{400 \\times 0.6 \\times 0.4}} \u2264 \\frac{x-np}{\\sqrt{npq}} \u2264 \\frac{240 -(400)(0.6)}{\\sqrt{400 \\times 0.6 \\times 0.4}}) \\\\\n\n= P(-8.57 \u2264 Z \u22640) \\\\\n\n=P(Z\u22640) -P(Z\u2264 -8.57) \\\\\n\n=0.5"
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