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ECONOMETRICS (ECON346)
1.
Distribution
The distribution of a data set is a table, graph, or formula that provides the values of the
observation and how often they occur (probability).
1.1 Distribution Shapes
•
The shape of a distribution can be described in terms of symmetry & kurtosis
•
With a symmetrical distribution a vertical line can be drawn through the middle
so that each side is a mirror image of the other.
•
With a skewed distribution the scores tend to pile up at one end and tail off at
the other.
•
If the tail is to the right the distribution is said to be positively skewed, if the tail
is to the left it is negatively skewed.
Symmetric Bellshaped
Right Skewed (Positive Skewed)
Left Skewed (Negative Skewed)
Bimodal
1.2
1.2
1.2 Population Distribution
Population Distribution
Population Distribution in Real World
in Real World
in Real World
In statistics, we face many normal distributions, but it is very hard to see them
in real world or mostly not known. This is many challenges that we need to
think about.
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•
Income Distribution (Poverty, inequality and the distribution of income
inthe Group of 20 by Xavier SalaiMartin and Sanket Mohapatra (2003)
(http://www.g20.org/Documents/poverty_and_inequality_g20.pdf)
ECONOMETRICS (ECON346)
•
Cook County Income Distribution
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2.
SAMPLING
Population
: The entire group of items that interests us. Defined by the characteristics
Sample
: The part of population that actually observed.
Why sampling
To draw inferences about the population since it is often impractical to
scrutinize the entire population. It is too expensive to apply to the entire population.
Biased Sample
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This note was uploaded on 02/16/2011 for the course BUS 355 taught by Professor White during the Spring '11 term at UChicago.
 Spring '11
 white
 Econometrics

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