Random samples of monthly rent prices in dollars for studio

Random samples of monthly rent prices, in dollars, for studio and one-bedroom apartments, were obtained for the Pennsylvania cities of Harrisburg and Philadelphia in July 2007. A 90% confidence interval for the difference in population means

Solution

Determine the midpoint of this interval.

(-261.1+22.3)/2 = -119.4

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Determine the half-width of this interval.

(261.1-22.3)/2 = 119.4

There is a significant average difference between rents in Harrisburg and Philadelphia because the interval does not include 0.

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(3) the half-width becomes larger because the value of Z is larger. But midpoint stays the same.

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(4) the midpoint becomes larger, but half-width stays the same.