Up to Exam 2 Flashcards
Four scales of measurements
Nominal scale : one object is different from another
Ordinal scale : one object is bigger or better or more of anything than another
Interval scale : one object is so many units (degrees ect) more than another
Ratio scale : Interval scale with an absolute zero
Validity and Reliability of Measures
Validity = the extent to which a measurement instrument measures what it is intended to measure
Reliability = the consistency with which a measurement instrument yields a certain result when the entity being measured hasn’t changed
what is cross - level analysis
researchers use data collected for one unit of analysis to make inferences about another unit of analysis
two reasons why one would use cross level analysis: cost and availability issues
what is ecological inferences
cross level analysis goal = using aggregate data to study the behavior of individuals
Relationship between schools average test scores and percentage of children receiving subsidized
what is ecological fallacy
NOT IN BOOK
it is the use of information that shows a relationship for groups to infer that the same relationship exists for individuals when in fact there is no such relationship at the individual level
Ecological Fallacy = a flaw
example: group x has characteristic y. person 1 is in group x, so that person must have characteristic y.
defining statements about concepts
six
concepts help us observe and understand aspects of our environment and help us communicate with others
a word or symbol that represents some idea
contributed to the identification and delineation of the scientific disciplines within which research is conducted
are developed through a process by which some human group (tribe, nation) agrees to give a phenomenon or a property a particular name
disappear from a group’s language when they are not longer needed, and ew ones are invented as a new phenomena are noticed that require names
we use concepts everyday to help cope with the complexity of reality by categorizing the things we encounter according to some of their properties that are relevant to us.
a concept is
a word or symbol that represents some idea
do we use concepts everyday?
yes
we use concepts everyday to help cope with the complexity of reality by categorizing the things we encounter according to some of their properties that are relevant to us
concepts in social science and in everyday
Social science concepts serve the same purpose as everyday concepts
they point to the properities of objects (people, political systems) that are relevant to particular inquiry. One observer might be interested in a a person’s personality structure, another is interested in partisan identification, and a third focuses on the person’s level of political alienation
the person has all of these properties and many more but only certain of the properties are relevant to any given piece of research
all three observers are dealing with he same reality; they simply choose to organize their perceptions of it differently.
Three Definitions: Concepts
Three things a concept must be
concepts help us to decide which of the many traits or attributes are important to our research
concepts, like theories, do not have a life of their own.
concepts are tools we create for specific purposes and cannot be labeled true or false, but only more or less useful.
Concepts must be
precise, accurate, informative
what makes a concept useful
the concept must refer to phenomena that are at least potentially Observable
a concept must refer to something that can be measured with our ordinary senses
examples of concepts
people simply do not have a class status in the way they have red hair, but if we know certain things about them (income, occupation) we can infer what their class status is
question about concepts
can we devise a set of procedures for using our senses to gather information that will allow us to judge the presence or absence of magnitude int he real world of the thing to which the Concept refers?
Empirical referents
if we can do this for a concept, it is said to have an empirical referents; it refers to something that is directly or indirectly observable
why is precision important in concepts?
it tells us what to observe in order to see how a concept is manifested in any given case
what is a theoretical import
a concept has a theoretical import
a concept has a theoretical import when it is related to enough other concepts in the theory that it play an essential role in the explanation of observed events
operationalization
deciding how to record empirical observations of the occurrence of an attribute or a behavior using numerals or scores
conceptualization to operationalization
researchers must define the concepts they use in their hypotheses through Conceptualization. they also must decide how to measure the presence, absence, or the amount of these concepts in the real world.
Political scientists refer to this process as Operationalization
operational definitions are…
seldom absolutely correct or incorrect
are evaluated according to how well they correspond to the concepts they are meant to measure
***Arriving at the operational definition is the last stage in the process of defining a concept precisely **
measurement
the process by which phenomena is observed systematically and represented by scores or numerals
test retest method of reliability
applying the same “test” to the same observations after a period of time and then comparing the results of the different measurements
same score over time over and over again
Difficulty arises when our measure involves interviewing people (as opposed to inanimate objects) if we repeat questions in a short time, interviewees may. remember their first answer and, in effort to be consistent, repeat that answer rather than respond truthfully in answering the question.
this can be problematic because what’s being measured can change, it is not unreliable
alternative form method of reliability
measuring the same attribute more than once but uses two different measures of the same concept rather than the same measure.
using two sets of questions about the same topic and seeing if the answers are reliable
different forms of the measure are applied to the same group of cases, or the same measure is applied to different groups at the same time.
if we can assume that these conditions are met, the more the score on the two measures, or the score of the two groups, are alike, the more confidence we have in the reliability of our measure.
If we cannot come up with comparable measures or groups, we cannot use the method properly
split-halves method of reliability
applying two measures of the same concept at the same time.
used with multi-item measures that can be split in two halves
in a survey, five questions represent one measure of the topic and the other represent a second half. if the scores are similar, the ten item measure is reliable
this methods avoids the problem that the concept being measured ay change between measures. Often used when a multi-item measure can be split into two equivalent halves.
validity
the degree of correspondence between the measure and concept it is thought to measure
Unlike reliability, which depends on whether repeated applications the same or equivalent measures yield the same results.
voting: always over estimated because of self-reported voting
invalid if it measures a slightly or very different concept than intended
more difficult to demonstrate empirically than reliability
face validity
asserted (not empirically demonstrated) when the measurement instrument appears to measure the concept it is supposed to measure.
measurements lack face validity when there are good reasons to question the correspondence of the measure to the concept in question. It is essentially a matter of judgement. if there is no consensus, the face validity is problematic
to assess the face validity of a measure we need to know the meaning of the concept being measured and whether the information being collected is relevant
Content validity
involves determining the full domain or meaning of a particular concept and then making sure all of the components of the meaning are included in the measure.
measuring democracy: two concepts political rights and civil liberties, eleven items in each. we must make sure that all eleven (twenty two) components in the definition
Content validity is similar to face validity but involves determining the full domain (whole content) or meaning of a particular concept and then making sure that ALL components of the meaning are including in the measure
Construct validity
Construct validation
is achieved by inferring the validity of a measure from evidence of the extent to which actual relationships between scores of various measures are consistent with what we expect from the theory that has led us to use a given indicator
Key term is inferring
two different ways to measure empirically
convergent construct validity
discriminant construct validity
convergent construct validity
measure of a concept is related to a measure of another concept with which the original concept is thought to be related.
two concepts ought to be related in a positive or negative manner. the researcher then develops a measure of each of the concepts and examines the relationship between them.
if one measure is positively or negatively correlated, then one measure has convergent validity for the other measure.
if there is no relationship between the measures, then the theoretical relationship is an error
discriminant construct validity
involves two measures that theoretically are expected to NOT be related; thus, the correlation between them is expected to be low or weak. If the measures do not correlate with one another, then discriminant construct validity is demonstrated
interitem association
the type of validity test most often used by political scientists
relies on the similarities of outcomes of more than one measure of a concept to demonstrate the validity of the entire measurement scheme because just one measure is more prone to error or misclassification of a case
correlation matrix
shows how strongly related each of the items in the measurement scheme is to all the other items.
random measurement error
an error in measurement that has no systematic direction or cause
what would happen if you had inaccurate measurements in your research?
inaccurate measurements may lead to erroneous conclusions, since they will interfere with our availability to observe the actual relationship between two or more variables
what are the two major threats to the accuracy of measurements?
measures may be unreliable or invalid
what does an unreliable measure produce?
an unreliable measure that produces inconsistent results– sometimes higher sometimes lower
what is reliability?
describes the consistency of results from a procedure or measure in repeated tests or trials
in the context of measurement, a reliable measure is one that produces the same result each time the measure is used
Can we get the same value for any given case when we apply the measure several different times, or does each application result in the assignment of a different value to each case?
a measure may be reliable without being valid BUT
it cannot be valid without being reliable.
systematic and random error in validity and reliability
validity is challenged by both systematic and random error, but reliability is jeopardized only by random error
This means that if a measure have convincingly validated in prior studies, we can use it without being worried about its reliability; it has to be reliable if it is valid.
how do we guard against unreliability?
preventing unreliability depends on our being aware of the various sources of random measurement error and doing what we can to control them
Catch it before it happens
how do we determine whether or not a given measure is reliable?
PRETESTING
thinking through the actual measurement process and pretesting our measuring instruments to discover previously unrecognized causes of random error
pretest= smaller sample size
why is it difficult to determine whether or not we have devised a reliable measure in the social sciences?
the true value of the variables with which we are concerned can change dramatically with time and circumstance– people change their opinions
it is hard to distinguish the effects of random measurement error from genuine fluctuations in the concepts being measured.
So, tests of reliability should be conducted over a short period of time.
Steps to the split halves method
administer the test to a large group of students (ideally, over 30)
randomly divide the test question into two parts. separate even and odd questions
score each half of the test for each student
find the correlation coefficient for the two halves
Split halves
NOT FROM TEXT BOOK
used for measuring the internal consistency of the test
it measures the extent to which all parts of the test contribute equally
a test or group is divided into two parts
scores collected from two half tests or two parallel groups
Nominal measurement
provides the LEAST amount of information about a phenomenon
Nominal measurement is obtained by simple naming cases by some predetermined scheme of classification
Nationality is typically measured at the nominal level by classifying people as Swiss, American eat.
That measurement neither tells us how much of the characteristic nationality different individuals have nor allows us to rank-order them
Using nominal measurement simply gives us a way of sorting cases into groups designated by the names used in a. classificatory scheme
Ordinal measurement
provides more information because it allows us both to categorize and to order, or rank, phenomena
ordinal measurement allows us to associate a number with each case. That number tells us not only that the cause is different from some there cases, and similar to still others (with respect to the variable being measured) but also how it relates to those other cases in terms of how much of a particular property it exhibits
With ordinal measurement we cans ay which cases have more or less of the measured quality that other cases and we can rank cases in the order of how much of the quality they exhibit
that ranking gives us more detailed and precise information about the cases than we would get from a nominal measurement
Interval measurement
NOT IN TEXTBOOK
Provides even more information
We can classify and rank order cases when they have been measured at the Interval level, we can also tell HOW MUCH (or less) of the measured property they contain than other cases
Ordinal measurement is NOT based on standardized unit of the variable in question and does NOT allow us to tell how far cases are from one another in terms of that variable. It allows us ONLY to say that some have more or less of it than others.
Interval measurement is based on the idea that there is some Standard Unit of the property being measured.
Interval measurement provides information on the “distance” between cases
Levels of Measurement
measuring procedures provide a means of categorizing and ordering phenomena
Some procedures produce more precise and detailed distinctions between events than do others. Because of this, there are various Levels of Measurements
When we say a procedure produces a given level of Measurement, we are classifying it according to how much information it gives us about the phenomena being Measured and their relationship to one another
Sets needed to make nominal measurement useful
NOT IN TEXTBOOK
to be useful, nominal measurement schemes must be based on sets that are Mutually Exclusive and Collectively Exhausive
It must not be possible to assign any single case to more than one category
the categories should be set up so that ALL cases can be assigned to some category
Nominal example: US voters
NOT IN TEXTBOOK
if we want to classify voters in the US by use of a nominal measuring scheme, we cannot use the categories democratic republic liberal and conservative successfully because these categories are not mutually exclusive
Since US political parties each appeal to a broad spectrum of voters, it is possible for a person to be both DEM and conservatives or liberal, or both a. Republican and a conservative or liberal
the categories do not allow us to differentiate among voters in all cases
If we try to categorize voters by party affiliation using only two categories-repub and dem- we will find that our categories are not collectively exhaustive, because some voters consider themselves independents or members of other parties