
reliability
consistently gives the same answer

validity
 measures what it is supposed to measure
 accuracy

internal validity
the study really investigates the proposed question

external validity
how well the study results are generalized across populations, settings and time

population
entire group or class of subjects, variables, concepts, or phenomena

census
process of examining every member of a population

sample
a subset that is taken to be representative of the entire population

probability sample
 selected according to mathematical guidelines whereby the chance for selection of each unit is known
 quantitative

nonprobability sample
 selected for convenience of the researcher
 qualitative research

convenience sample
 available sample
 ex. group of students in mass media

volunteer sample
individuals are not selected mathematically

purposive sample
subjects selected on basis of specific characteristics

quota sample
subjects selected tot meet a predetermined or known percentage

quota sample example
ex. survey composed of 10% VCR owners and 90% nonVCR owners reflects the population characteristics

Network (snowball) sample
based on other sample member's referrals

random sample
each subject in pop has an equal chance of selectoin

random sample example
ex. reading table of numbers

systematic sampling
every nth subject is selected from a population

systematic sample example
ex. blocks of 4 people and then every third person within that block

sampling frame
complete list of members in the pop of sample

periodicity
the order of the items in the pop list may bias selection

periodicity example
ex. every 10th tv program from a list may be an ABC program

stratified sampling
used to guarantee a subsample of the population is represented; homogenous

stratified sample example
ex. graduate students out of all students

larger
sample size: the ______, the better

independent variables
predictor variables

dependent variables
criterion variables

operational definition
 specifies procedures to be followed in measuring a concept; clear statement about what is to be observed
 how the variable is measured

operational definition
ex. go to the grocery store and see sign for milk; go to sign and what's underneath it is milk

constitutive definition
defines a construct using other constructs (like a dictionary)

construct
a term that expresses an abstract idea formed by generalizing from particulars and summarizing related observations.

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

continuous variable
can take on any value, including fractions; can be meaningfully broken into smaller subsections

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

discrete variables
includes only a finite set of values; cannot be divided into subparts

discrete variables examples
number of children in family (bc the unit is a person); political affiliation; gender of a person; population

nominal
numerals or other symbols are used to classify people, objects, or characteristics; labels that stand for the respective categories, have no significance

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

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

ordinal measurement example
ex. “socioeconomic status” – categorizing families according to class: lower, lower middle, middle, upper middle, upper

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)

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.

ratio
 interval properties
 has true zero

ratio measurement example
Time spent watching TV or number of words per story

qualitative research
methods of data collection including focus groups, field observation, indepth interviews, case studies, etc

quantitative research
 variables under consideration must be measured
 large samples often used to generalize results

likert scale
uses interval measurement for scale in which respondents strongly agree, agree, are neutral, disagree, or strongly disagree with the statements

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

