Data collection
methods
observation – participant, nonparticipant,
unobtrusive
interviewing - self-administered questionnaires,
face-to-face/telephone interviews, computer-assisted
records/documents/archives
More on measurement
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error - variation in repeated measurements;
also imprecision
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bias - systematic error - affects all
measurements in the same direction
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measured value = actual value + chance
error + bias
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univariate - single variable
-
bivariate - relationships between two
variables
-
multivariate - relationships among
3+ variables
hypotheses are predictions about the
value of a particular variable or relationships between variables
Research design
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experimental vs. observational designs
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experimental - researcher manipulates
a variable to test causal relationship (does X cause Y?)
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random assignment to one or another
group
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practical & ethical limitations
to experiments
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observational (nonexperimental) - researcher
simply "observes" world
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cross-sectional vs. longitudinal
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cross-sectional = one point in time
-
longitudinal = same sample followed
over time
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time series
Summary
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populations, samples, sampling
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data collection methods - interviewing,
observation, archival records
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experimental vs. observational
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cross-sectional vs. longitudinal
"3 out of 4 Americans make up 75% of
the population."
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cases = elements of/units in sample
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frequency = number of cases with a
particular value
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relative frequency = proportion of
total
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percentage = proportion x 100; proportion
= percentage / 100
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rate - # events in period divided by
total population
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higher rates for longer time periods
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event can happen to an individual more
than once in a period
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# events could exceed population total