HW_03_04_SOLN - ECO220Y: Homework, Lectures 3 & 4 SOLUTIONS...

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Page 1 of 2 ECO220Y: Homework, Lectures 3 & 4 – SOLUTIONS (1) Symmetric, bell shaped, unimodal. Resist the temptation to call this bimodal and positively skewed: it is not. When we are describing the shape we see in a histogram we are trying to make inferences about the distribution of the population. However, the histogram is based on a SAMPLE: samples are subject to sampling noise. We do NOT want our conclusions to be driven by sampling noise. This means that we should look for major trends in the histogram and not get worked up about small deviations from the ideal bell shape: there will often be small deviations due to sampling noise. We will never see a perfect bell shape in a sample even if the sample is taken from a perfect bell shaped population. Modality refers to MAJOR PEAKS: the reason for the word “major” is to avoid counting up every small peak that can happen with sampling noise. Exactly 30 (13.2%) of the observations are less than 0, but you can’t figure that exact number out with the given information. Just eye-balling the picture, you should get an answer between 10 – 50 observations
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This note was uploaded on 03/01/2011 for the course ECON 220 taught by Professor Tanaka during the Spring '11 term at University of Toronto- Toronto.

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HW_03_04_SOLN - ECO220Y: Homework, Lectures 3 & 4 SOLUTIONS...

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