Chapter 4 Study Questions
for Statistics, Freedman et al.
ISA Statistics, Prof. Janeba
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Section 4.1
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Name two measures that give the center of a set of data.
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Name two measures that give the spread of a set of data.
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Which example shows that knowing the center for a dataset doesn't tell
you all about the dataset?
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Which example shows that knowing both the center and the spread doesn't
tell you all you'd want to know?
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If center and spread aren't enough to know, what's another method of summarizing
data that tells us much more?
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Section 4.2
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Why oughtn't we conclude from figure 3 that as people age, their heights
go down steadily starting in their 20's, while their weights go up and
then down?
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Section 4.3
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What do you look for in a histogram to estimate the average? What
about estimating the median instead?
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Which is more greatly affected by a single datum much larger than the rest
- the average or the median? (see figure 6)
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For histograms with long tails on one side: which is farther out
on the tail - the average or the median? (see figure 7)
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Section 4.4
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Expand the phrase Root mean square into a larger expression that
describes more fully what RMS means.
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Make sure you can actually compute the RMS of a list of numbers.
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Section 4.5
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Write a careful sentence that gives the precise relationship between the
Standard Deviation and RMS.
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What, roughly, does the SD tell us about a list of numbers?
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(From class) If we want the "typical deviation size", why not just average
the deviations?
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What is the "rule of thumb" about SD's - how much of a list is typically
within one SD of the average?
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Continue the "rule of thumb" from the previous question (see box on p.
68, and note third part given in class).
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How often does this "rule of thumb" actually work?
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Section 4.6,4.7
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Make sure you can actually compute the SD of a list of numbers, both by
hand and with your calculator.
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For help using many popular calculators, see my
help files.
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When is the SD of a list equal to zero?
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If all the numbers in a list are exactly 5 units away from the list's average,
then the SD will be ...
Last Modified February 1, 2000.
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