Research Methods in Crime and Justice

1. Research Methods in Crime and Justice Chapter 6 Measurement

2. Measurement • Measurement is the process by which social science researchers determine how to assess the social phenomena they study. • Measurement in social science research is more difficult than in physical science research because social concepts and phenomena are more challenging to define.

3. Conceptualization • The measurement process begins with conceptualization. • Conceptualization is the process by which researchers develop precise definitions of the concepts they study.

4. Operationalization • Operationalization begins after the concepts have been defined. • Operationalization is the process by which a researcher decides how to actually measure the variables as they are defined conceptually.

5. Levels of Measurement • A variable is anything that varies. • Race or ethnicity • Height • Income • All variables have attributes. • Attributes are the levels or variations of a variable. • The variable ‘gender’ has two attributes – ‘male’ and ‘female’. • Variables are discussed in more detail in Chapter 7.

6. Levels of Measurement • The level at which a variable is measured has important implications. • Generally speaking, higher levels of measurement are more precise. • The level at which we measure variables determines how we analyze the data that we collect during our research.

7. Levels of Measurement • There are four levels of measurement. • Nominal • Ordinal • Interval • Ratio

8. Nominal • The lowest level of measurement • Nominal level variables are merely names or labels. • The attributes (i.e. the categories) of nominal level variables cannot be arranged in any logical order or sequence. • Examples: Race, ethnicity, gender

9. Ordinal • Like nominal level variables, ordinal level variables are also names or labels. • In addition, the attributes of an ordinal level variable can be rank ordered, or arranged in a logical order. • Examples: Race results – first place, second place, and third place winners.

10. Interval • Like nominal level variables, interval level variables can be names or labels. • Like ordinal level variables, the attributes of an interval level variable can be rank ordered, or arranged in a logical order. • In addition, the distances between the attributes of an interval level variable are equal. • Examples: height, weight, age

11. Ratio • Like nominal level variables, ratio level variables can be names or labels. • Like ordinal level variables, the attributes of a ratio level variable can be rank ordered, or arranged in a logical order. • Like interval level variables the distances between the attributes of a ratio level variable are equal. • In addition, ratio level variables include an absolute zero. • Examples: income, temperature

12. Levels of Measurement

13. Levels of Measurement • It is possible to convert a variable originally measured at a higher level of measurement into a variable measured at a lower level of measurement. • It is not possible to convert a variable originally measured at a lower level of measurement into a variable measured at a higher level of measurement.

14. Levels of Measurement • An alternative method for classifying the levels of measurement. • Discrete variables • similar to nominal and ordinal level measures. • Fixed number of attributes • Continuous variables • Similar to interval or ratio level variables. • Almost unlimited number of attributes.

15. Validity and Reliability • Social scientists evaluate the quality of their measures based on their validity and reliability. • Validity refers to the ability of a measure to accurately measure the concept it claims to measure. • Reliability refers to the ability of a measure to consistently measure the concept it claims to measure.

16. Validity • There are four commonly used methods for assessing the validity (accuracy) of a measure. • Face validity • Criterion or predictive validity • Construct validity • Content validity

17. Face Validity • Refers to whether a measure appears to be valid on its face, or whether it makes sense. • For example, if we measure a person’s lifetime level of criminal behavior using only their adult criminal convictions, our measure would not have face validity because it excludes juvenile criminal convictions.

18. Criterion or Predictive Validity • Refers to the extent to which a measure relates to another, more direct measure of the same concept. • For example, we might ask someone whether they have been arrested for a crime and test the criterion validity of this measure by comparing their answers to official arrest records.

19. Construct Validity • Refers to the extent to which a measure corresponds to other variables that are related to the underlying variable we are interested in studying. • For example, there appears to be a relationship between creditworthiness and criminal behavior. • So, one might ask if a credit score has construct validity with criminal behavior.

20. Content Validity • Refers to the degree to which a measure includes every dimension of the concept. • For example, individuals with strong social bonds (marriage, parenthood and friendships) are less likely to commit crime • So, if we wanted to ensure that our measure of social bonds has content validity, we would have to include all of these dimensions, and maybe more.

21. Reliability • There are four commonly used methods for assessing the reliability (consistency) of a measure. • Test-Retest • Inter-rater • Split half • Concurrent (benchmarks/baselines

22. Test-Retest • The test-retest method requires a researcher to administer a measure twice to the same group to see of the results are similar. • The measure is considered reliable if the results from each test administration are similar.

23. Inter-rater • To use the inter-rater method a researcher would ask two or more researchers to observe and measure the same thing. • Then the researcher would compare the results to see if they generally have the same impression of what they observed. • If so, then the measure is considered reliable.

24. Split half • The split half reliability method requires a researcher to split a measure in half (or develop a similar measure) and administer each half to two similar groups. • The measure is considered reliable if the results from each half are similar.

25. Concurrent(Benchmarks/Baselines) • The reliability of a new measure can be assessed with pre-existing benchmarks and baselines. • Often called concurrent reliability. • This simply means that the results from a new measure concur with the results from a pre-established and generally accepted measure of the same concept.

26. Indexes, Scales and Typologies • Indexes, scales and typologies enable researchers to collect detailed information about complicated social phenomena within a single measure. • These measurement devices are a great way of summarizing a lot of information into a single number.

27. Index • An index is a single number that represents a compilation of other measures. • The most common index used in criminal justice is the Crime Index calculated by the Federal Bureau of Investigation. • The FBI uses eight crime categories to calculate an overall rate of crime for each community, state, region and the nation.

28. Scale • A scale is a method for quantitatively measuring a single phenomenon or variable. • The most common types of scales are Likert scales, usually consisting of five points. • Strongly disagree • Disagree • Neither agree nor disagree • Agree • Strongly disagree

29. Typology • A typology is a method for classifying observations, people or situations into nominal categories. • Typologies are often used in qualitative research.

30. Quantitative vs. Qualitative • Quantitative measures are more common in criminal justice research. • There is a large and growing body of research that is qualitative in nature. • Some researchers erroneously assume that qualitative measures are less precise than quantitative measures. • This is probably because qualitative measures do not involve numbers.

31. Quantitative vs. Qualitative • But it is possible that the opposite is true. • Because they do not rely on numbers, qualitative measures are more difficult to operationalize. • This often forces qualitative researchers to be more precise and develop a deeper understanding of the phenomenon.

32. Getting to the Point • Measurement is a process by which social science researchers determine how to assess the social phenomena they study. • Conceptualization is the process by which researchers develop precise definitions for vague concepts. • Operationalization is the process by which researchers decide how to measure the variables as they are defined conceptually.

33. Getting to the Point • The level at which a variable is measured has important implications. Generally speaking, higher levels of measurement provide more detailed information and allow for more precise analytical techniques.

34. Getting to the Point • In the social sciences there are four levels of measurement: nominal, ordinal, interval and ratio.

35. Getting to the Point • Nominal level variables are merely names or categories. • The attributes of nominally measured variables cannot be arranged in any logical order or sequence.

36. Getting to the Point • Ordinal level variables are also names. • In addition the attributes of an ordinal level variable can be ordered in a logical sequence.

37. Getting to the Point • The attributes of interval level variables can also be arranged in a logical order. • In addition, interval level variables have equal differences between their attributes.

38. Getting to the Point • Ratio level variables have the same characteristics as interval level variables. • In addition, the attributes of ratio level variables include an absolute zero.

39. Getting to the Point • It is possible to convert a variable measured at a higher level of measurement into a variable measured at a lower level of measurement. • It is not possible to convert a variable measured at a lower level of measurement into a variable measured at a higher level of measurement.

40. Getting to the Point • Social scientists rely on the concepts of validity and reliability in order to improve the quality of their measures.

41. Getting to the Point • Validity refers to the ability of a measure to accurately measure the concept it claims to measure. • There are four commonly used methods for assessing the validity (accuracy) of a measure. • Face validity • Criterion or predictive validity • Construct validity • Content validity

42. Getting to the Point • Reliability refers to the ability of a measure to consistently measure the concept it claims to measure. • There are four commonly used methods for assessing the reliability (consistency) of a measure. • Test-Retest • Inter-rater • Split half • Concurrent (benchmarks/baselines)

43. Getting to the Point • An index is a measurement device that compiles various measures into a single number. • A scale is a method for quantitatively measuring a single phenomenon or variable using a rating system. • A typology is a method for classifying observations, people or situations into nominal categories

44. Getting to the Point • Quantitative measures rely on numbers. • Qualitative measures rely on descriptions to measure social phenomena. • Often both are necessary to fully understand a concept.

45. Research Methods in Crime and Justice Chapter 6 Measurement