Stats: Modeling the World - Bock, Velleman, & DeVeaux
Chapter 10: Re-expressing Data
Key Vocabulary:
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Re-expression
Calculator Skills:
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log(
ln(
LnReg
ExpReg
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PwrReg
QuadReg
CubicReg
1. What is meant by re-expressing data?
Re-express the data by tahing the log, square root, reciprocal
2. One of the goals of re-expressing data is to make the distribution appear more symmetric.
Why is this advantageous?
It is easier to summarize the center of a symmetric distribution
3. Another goal of re-expressing data is to make the spread of several groups more alike. Why
is this advantageous?
Groups that share a common spread are easier to compare
4. Why is it advantageous to make the form of a scatterplot more nearly linear?
Easier to describe
5. What type of data often benefits from re-expression by squaring values?
Unimodal distributions that are skewed to the left
6. What type of data often benefits from re-expression by taking the square root of values?
Counts
7. What type of data often benefits from re-expression by taking the logarithm of values?
Measurements that cannot be negative
8. What type of data often benefits from re-expression by taking the reciprocal of values?
Chapter 10: Re-expressing Data
Stats: Modeling the World - Bock, Velleman, & DeVeaux
9. If your data contain zeroes, what must you do before re-expressing using logarithms or
reciprocals? Explain.
Try adding a small constant to all values
10. If a scatterplot of the x-values vs. the logarithm of the y-values appears to be linear, what
type of relationship is there between the original x- and y-values?
exponential
11. Rewrite yˆ  ab x in linear form.
12. If a scatterplot of the logarithm of the x-values vs. the logarithm of the y-values appears to be
linear, what type of relationship is there between the original x- and y-values?
power
13. Rewrite yˆ  axb in linear form.
log yˆ  a  b log x
14. If a scatterplot of the logarithm of the x-values vs. the y-values appears to be linear, what
type of relationship is there between the original x- and y-values?
Logarithmic
15. Rewrite yˆ  a  b ln x in linear form.
Chapter 10: Re-expressing Data