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Types of Statistics
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Descriptive
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"Inside the Box" |
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Describes a specific set of data |
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e.g., mean |
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Inferential
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"Outside the Box" |
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Developed to take chance into
consideration when making predictions |
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Populations & Samples
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Populations - All members on any given
or defined group |
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Sample - A subset of any given or
defined population |
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Examples
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Our class might be a sample of the
following population
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All students taking
statistics |
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All students taking
statistics on Saturday |
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All students taking
statistics on Saturday in Houston |
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etc., etc., etc. |
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Our class might also be a
population if... we decided that the population was our class |
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Parameters & Statistics
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Parameters - a quantitative or
qualitative characteristic of a population |
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Statistics - a quantitative or
qualitative characteristic of a sample |
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Upper & Lower limits
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Quantitative variables have upper and
lower limits |
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The lower limit is found by subtracting
half a unit of measurement, while the upper limit is found by adding
half a unit of measurement |
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Examples
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73
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Upper limit = 73.5 |
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Lower limit = 72.5 |
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9.35
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Upper limit = 9.355 |
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Lower limit = 9.345 |
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Measurement Scales
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Nominal
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No real quantitative value |
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Numbers may be used, but they are
meaningless |
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Examples
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Sex - Male/Female (You can't
take the mean of sex) |
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Ethnicity -
Asian/Black/Hispanic/White (You can't take the mean of
ethnicity) |
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Ordinal
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Classification and ranking |
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One is simply greater or less than
another |
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There is no equal distance between
units of measurement |
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Examples
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Freshman, Sophomore, Junior,
Senior |
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1st place, 2nd place, 3rd
place, 4th place |
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Interval
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The intervals between the units of
measurement are equal |
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No true/real zero |
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Example - Fahrenheit |
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Ratio
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Equal intervals between units of
measurement |
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Has a true/real zero |
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Example - $$$ (zero means zero!) |
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Can be multiplied, divided, added,
subtracted, etc. |
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Experimental Design terminology
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Independent Variables - The variables
that are manipulated |
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Dependent Variables - The variables that
are measured or observed. The values of the dependent
variables depend on the independent variables |
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Extraneous Variables - Other variables
that might be possible for changes in the dependent variable |
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