1. Bell Ringer Using female = 0 and male = 1, calculate the average maleness in this classroom.

2. Levels of Measurement NOIR and your Survey Questions

3. Nominal Nominal Level of Measurement At the nominal level of measurement, numbers or other symbols are assigned to a set of categories for the purpose of naming, labeling, or classifying the observations. Gender is an example of a nominal level variable. Using the numbers 0 and 1, for instance, we can classify our observations into the categories "females" and "males," with 0 representing females and 1 representing males. We do not imply anything about the magnitude or quantitative difference between the categories. We cannot manipulate these quantities, i.e. what is average maleness of this class?

4. Nominal-Example Gender is an example of a nominal level variable. Using the numbers 0 and 1, for instance, we can classify our observations into the categories "females" and "males," with 0 representing females and 1 representing males. We do not imply anything about the magnitude or quantitative difference between the categories. We cannot manipulate these quantities, i.e. what is average maleness of this class?

5. Ordinal Whenever we assign numbers to rank- ordered categories ranging from low to high, we have an ordinal level variable. Ordinal = order

6. Ordinal- Example Social class is an example of an ordinal variable. We might classify individuals with respect to their social class status as "upper class", "middle class", or "working class". "upper class" has a higher class position than a person in a "middle class" category "upper class" has a higher class position than a person in a "middle class" category do not know the magnitude of the differences between the categories; that is, we don't know how much higher "upper class" is compared to "middle class". do not know the magnitude of the differences between the categories; that is, we don't know how much higher "upper class" is compared to "middle class".

7. Interval/Ratio If the categories (or values) of a variable can be rank-ordered, and if the measurements for all the cases are expressed in the same units, then an interval-ratio level of measurement has been achieved.

8. Interval-Example Examples of variables measured at the interval-ratio level are age, income, and SAT scores. With all these variables we can compare values not only in terms of which is larger or smaller, but also in terms of how much larger or smaller one is compared with another.

9. Interval – Ratio Distinction In some discussions of levels of measurement you will see a distinction made between interval-ratio variables that have a natural zero point (where zero means the absence of the property) and those variables that have zero as an arbitrary point. Weight and length have a natural zero point, whereas temperature has an arbitrary zero point (C vs. K). Variables with a natural zero point are also called ratio variables.

10. NOIR

11. Scales (levels) of Measurement To determine level of measurement Step #1 Identify the Unit of Observation (obs unit) (sampling unit) –(one of something)  What you are interested on studying? -individual (participant) for psychologists - Other possible Observational units: –A rat –A Group/team –A Household –A City –A Country –A College student

12. Scales (Levels) of Measurement To determine level of measurement Step #2 Ask: “What am going to do with the Obs unit?” Step #2 Ask: “What am going to do with the Obs unit?” –Two options:  Option A: Assign the Obs unit to a category (quality) –E.g. gender, race, social security number (unique)  Option B: Measure the Obs unit on some attribute or behavior –Intelligence, age, motivational level, number of hotdogs eaten

13. If Yes to Option A –If “Yes” to Option A  Ask: are the categories ranked on some quality? –E.g. job class (clerical I, II, III) –E.g. class standing (rank in class)  If “NO”, not ranked, then level of measurement is NOMINAL  If “Yes”, categories ranked, level of measure is ORDINAL

14. If Option B: Measure Obs Unit on some attribute or behavior Step #3 Identify Unit of Measure (Measurement Unit) –One of something (attribute or behavior)  E.g. item on a test, inventory –Ask: “Does the measure have a true zero? Usually:  Physical and behavioral ones do –E.g height, weight, number of cases sold  Psychological attributes do not –IQ, need for approval, depression level, attitude toward boss

15. Scales (Levels) of Measurement To determine level of measurement If answer to “Does the measure have a true zero?” If answer to “Does the measure have a true zero?” –Is “YES”, level is Ratio –Is “No”, level is Interval Try out a few: Try out a few:

16. What Level Measurement? Students Fail v. Pass Observational unit? Observational unit? –One student Place student in category? Place student in category? –Yes: fail or pass Are the categories ranked on some quality? Are the categories ranked on some quality? –Yes (underlying continuous variable…success in learning) Level of measurement? Level of measurement? –Ordinal

17. Now Practice Go to computer lab, log on to my wiki and click on link for today’s class 2/11. Complete exercises 1-10 and follow up question, record your answer on worksheet then check your answers.