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Chapter5
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- 2. •Because measurement isdifficult and imprecise, researchers try to describe the measurement process explicitly •We want to move from vague ideas of what we want to study to actually being able to recognize and measure it in the real world •Otherwise, we will be unable to communicate the relevance of our idea and findings to an audience 2
- 3. •Clarifying abstract mentalimages is an essential first step in measurement •“Crime” •Conception – Mental image we have about something •Concepts – Words, phrases, or symbols in language that are used to represent these mental images in communication •e.g., gender, punishment, chivalry, delinquency, poverty, intelligence, racism, sexism, assault, deviance, income 3
- 4. •Direct observables –Those things or qualities we can observe directly (color, shape) •Indirect observables – Require relatively more subtle, complex, or indirect observations for things that cannot be observed directly (reports, court transcripts, criminal history records) •Constructs – Theoretical creations; cannot be observed directly or indirectly; similar to Concept 4
- 5. •Specifying precisely whatwe mean when we use particular terms •Results in a set of indicators of what we have in mind •Indicates a presence or absence of the concept we are studying •Violent crime = offender uses force (or threatens to use force) against a victim 5
- 6. •Dimension – Specifiableaspect of a concept •“Crime Seriousness” – Can be subdivided into dimensions •e.g., Dimension – Victim harm •Indicators – Physical injury, economic loss, psychological consequences •Specification leads to deeper understanding 6
- 7. •Concepts are abstractand only mental creations •The terms we use to describe them do not have real and concrete meanings •What is poverty? delinquency? strain? •Reification – Process of regarding as real things that are not 7
- 8. •Conceptual definition (whatis SES?) •Working definition specifically assigned to a term, provides focus to our observations •Gives us a specific working definition so that readers will understand the concept •Operational definition (how will we measure SES?) •Spells out precisely how the concept will be measured 8
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- 10. •Operationalization – Theprocess of developing operational definitions •Moves us closer to measurement •Requires us to determine what might work as a data-collection method 10
- 11. •Measurement – Assigningnumbers or labels to units of analysis in order to represent the conceptual properties •Make observations, and assign scores to them •Difficult in CJ research because basic concepts are not perfectly definable 11
- 12. •Every variable shouldhave two important qualities: •Exhaustive – You should be able to classify every observation in terms of one of the attributes composing the variable •Mutually exclusive – You must be able to classify every observation in terms of one and only one attribute •Example: Employment status 12
- 13. •Nominal – Offernames or labels for characteristics (race, gender, state of residence) •Ordinal – Attributes can be logically rank- ordered (education, opinions, occupational status) •Interval – Meaningful distance between attributes (temperature, IQ) •Ratio – Has a true zero point (age, # of priors, sentence length, income) 13
- 14. •Certain analytic techniqueshave Levels of Measurement requirements •Ratio level can also be treated as Nominal, Ordinal, or Interval •You cannot convert a lower Level of Measurement to a higher one •Therefore, seek the highest Level of Measurement possible 14
- 15. •The key standardsfor measurement quality are reliability and validity •Measurements can be made with varying degrees of precision •Common sense dictates that the more precise, the better •However, you do not necessarily need complete precision 15
- 16. •Whether a particularmeasurement technique, repeatedly applied to the same object, would yield the same result each time •Problem – Even if the same result is retrieved, it may be incorrect every time •Reliability does not insure accuracy •Observer’s subjectivity might come into play 16
- 17. •Test-retest method –Make the same measurement more than once – should expect same response both times •Interrater reliability – Compare measurements from different raters; verify initial measurements •Split-half method – Make more than one measure of any concept; see if each measures the concept differently 17
- 18. •The extent towhich an empirical measure adequately reflects the meaning of the concept under consideration •Are you really measuring what you say you are measuring? •Demonstrating validity is more difficult than demonstrating reliability 18
- 19. •Face validity –On its face, does it seem valid? Does it jibe with our common agreements and mental images? •Criterion-related validity – Compares a measure to some external criterion •Construct validity – Whether your variable relates to another in the logically expected direction •Content validity – Does the measure cover the range of meanings included in the concept? •Multiple Measures – Alternative measures 19
- 20. •Allows us tocombine individual measures to produce more valid and reliable indicators •Reasons for using Composite Measures: •The researcher is often unable to develop single indicators of complex concepts •We may wish to use a rather refined ordinal measure of a variable, arranging cases in several ordinal categories from very low to very high on a variable such as degree of parental supervision •Indexes and scales are efficient devices for data analysis 20
- 21. •“Taxonomy” •Produced by theintersection of two or more variables to create a set of categories or types •e.g., Typology of Delinquent/Criminal Acts (Time 1 and 2) •None, Minor (theft of items worth less than $5, vandalism, fare evasion), Moderate (theft over $5, gang fighting, carrying weapons), Serious (car theft, breaking and entering, forced sex, selling drugs •Nondelinquent, Starter, Desistor, Stable, Deescalator, Escalator 21
- 22. •What is disorder?(Skogan, 1990) •Distinguish between physical presence & social perception • Physical disorder: Abandoned buildings, garbage and litter, graffiti, junk in vacant lots •Social disorder: Groups of loiterers, drug use and sales, vandalism, gang activity, public drinking, street harassment •Index created by averaging scores for each measure 22
- 23. •A composite indexis a more valid measure than a single question •Computing and averaging across all items in a category create more variation than we could obtain in any single item •Two indexes are more parsimonious than nine individual variables •Data analysis and interpretation can be more efficient 23