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reliability
consistently gives the same answer
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validity
- measures what it is supposed to measure
- accuracy
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internal validity
the study really investigates the proposed question
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external validity
how well the study results are generalized across populations, settings and time
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population
entire group or class of subjects, variables, concepts, or phenomena
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census
process of examining every member of a population
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sample
a subset that is taken to be representative of the entire population
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probability sample
- selected according to mathematical guidelines whereby the chance for selection of each unit is known
- quantitative
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non-probability sample
- selected for convenience of the researcher
- qualitative research
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convenience sample
- available sample
- ex. group of students in mass media
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volunteer sample
individuals are not selected mathematically
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purposive sample
subjects selected on basis of specific characteristics
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quota sample
subjects selected tot meet a predetermined or known percentage
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quota sample example
ex. survey composed of 10% VCR owners and 90% non-VCR owners reflects the population characteristics
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Network (snowball) sample
based on other sample member's referrals
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random sample
each subject in pop has an equal chance of selectoin
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random sample example
ex. reading table of numbers
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systematic sampling
every nth subject is selected from a population
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systematic sample example
ex. blocks of 4 people and then every third person within that block
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sampling frame
complete list of members in the pop of sample
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periodicity
the order of the items in the pop list may bias selection
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periodicity example
ex. every 10th tv program from a list may be an ABC program
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stratified sampling
used to guarantee a subsample of the population is represented; homogenous
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stratified sample example
ex. graduate students out of all students
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larger
sample size: the ______, the better
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independent variables
predictor variables
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dependent variables
criterion variables
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operational definition
- specifies procedures to be followed in measuring a concept; clear statement about what is to be observed
- how the variable is measured
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operational definition
ex. go to the grocery store and see sign for milk; go to sign and what's underneath it is milk
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constitutive definition
defines a construct using other constructs (like a dictionary)
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construct
a term that expresses an abstract idea formed by generalizing from particulars and summarizing related observations.
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construct examples
ex. table” – concept that represents a wide variety of observable objects, ranging from a plank supported by concrete blocks to a piece of furniture commonly found in dining rooms.“emo”“Taffies” – technologically advanced families
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continuous variable
can take on any value, including fractions; can be meaningfully broken into smaller subsections
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continuous variable examples
ex. height (can distinguish between 72.12 inches tall and 72.13 inches tall); time spent watching television (person A spent 3.12 hours watching while person B spent 3.13 hours); the average number of children in a family
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discrete variables
includes only a finite set of values; cannot be divided into subparts
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discrete variables examples
number of children in family (bc the unit is a person); political affiliation; gender of a person; population
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nominal
numerals or other symbols are used to classify people, objects, or characteristics; labels that stand for the respective categories, have no significance
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nominal measurement example
rocks can be classified into 3 categories: igneous, sedimentary, metamorphic. A scientist who assigns a 1 to igneous, a 2 to sedimentary, and a 3 to metamorphic has created a nominal scale
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ordinal
- ranked along some dimension, such as from smallest to largest;
- numbers generally have some mathematical meaning;
- equivalence – all in one category are treated equally
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ordinal measurement example
ex. “socioeconomic status” – categorizing families according to class: lower, lower middle, middle, upper middle, upper
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interval
- has all the properties of an ordinal scale and the intervals between adjacent points on the scale are of equal value;
- property of equal differences
- no true zero (can't have it)
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interval measurement example
ex. temperature – the same amount of heat is required to warm and object from 30 to 40 degrees as to warm it from 50 to 60 degrees.
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ratio
- interval properties
- has true zero
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ratio measurement example
Time spent watching TV or number of words per story
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qualitative research
methods of data collection including focus groups, field observation, in-depth interviews, case studies, etc
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quantitative research
- variables under consideration must be measured
- large samples often used to generalize results
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likert scale
uses interval measurement for scale in which respondents strongly agree, agree, are neutral, disagree, or strongly disagree with the statements
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semantic differential scale
uses interval measurement for scale consisting of 7 spaces between two bipolar adjectives (good___bad), asked to choose where his or her position lies
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