22s:152 Applied Linear Regression
Chapter 3: Examining Data————————————————————
Review types of data
Quantitative:
• Continuous weights, heights, i.e. ‘decimal’ values
• Discrete finite (or infinitely countable)number of values is
possible
‘counts’ fall into this category
Qualitative:
• Categorical/Nominalgender: male/female
color: green, blue, etc.
• Ordinal high/median/low1
Review terminology
• Variable– a particular characteristic that may take
on differet values for different subjects orexperimental
units.
e.g. age, weight, chemical make-up
• Dependent variable– the ‘response’ variable
– the thing we want to ‘predict’
• Independent variable– an explanatory variable (there may be
many)
– a variable used to predict the response
– can also be called ‘covariate’
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• Observation
– an observation is taken on a single subject,and corresponds to
a row in a data matrixor table such as this...
country infant.mortality gdp
-------- ---------------- ---
Afghanistan 154 2848
Albania 32 863
Algeria 44 1531
American.Samoa 11 NA
Andorra NA NA
Angola 124 355
– an observation includes independent anddependent variables
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Examining Data————————————————————Visual investigation of
numerical datais important (and very useful)
• Are there outliers?• Are there any ‘suspect’ data points?
40 60 80 100 120
4060
8010
012
014
016
0
reported weight
actu
al w
eigh
t
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malesfemales
Davis, C. (1990) Body image and weight preoccupation: A com-
parison between exercising and non-exercising women.
Appetite,
15, 1321.
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