One or more variables (characteristics of the population units) that are to
be investigated
The sample of population units
The inference about the population based on information contained in the
sample
A measure of reliability for the inference
•
Section 5
o
Types of data
Quantitative data – measurements recorded on a naturally occurring
numerical scale
Qualitative data – measurements cannot be measured on natural numerical
scale
•
Only be classified into one of a group of categories
•
Section 6
o
Collecting data
From published source (newspaper, book)
Designed experiment (lab)
Survey
Collected observationally
o
Samples
Representative sample exhibits characteristics typical of these possessed
by the population of interest
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Random sample – selected from population that every different sample has
equal chance of selection
•
Section 7
o
Statistical thinking
Applying rational thought of science to assess data and inferences
Fundamental to the thought process is that variation exists in populations
and process data
o
Nonrandom sample errors
Selection bias results when subset of experimental units in the population
is excluded so that these units have no chance of being selected for the
sample
o
Nonresponse bias: researchers conducting a survey or study are unable to obtain
data on all experimental units selected for sample
o
Measured error: inaccuracies in value of data recorded
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 Fall '12
 JagbirSingh
 Statistics

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