1. Raymond Martin rmartin@utech.edu.jm

3. Lecture 6 – Measurement Data are: – pieces of observable information –limited by measurement Measurement is: –limiting the data

4. Lecture 6 – Measurement Cont’d Two types of measurement – Substantial measurement e.g. area measurement of observable information (variables) –Insubstantial measurement Exists only as concepts (opinions, ideas, feelings) e.g. status

5. Lecture 6 – Measurement Cont’d The process of formulating and clarifying concepts into measurable variables is called conceptualisation. – e.g. The concept status can be linked to ownership of property Operationalisation develops an expression of what a concept means using operational definitions. –e.g. Upper class means owns home and lower class means rents home.

6. Lecture 6 – Measurement Cont’d A constant is a characteristic that is the same for all subjects under study while… a variable is a characteristic that takes on different values for subjects under study.

7. Lecture 6 – Measurement Cont’d Identify the constants and the variables

8. Lecture 6 – Measurement Cont’d An Independent variable influences while a Dependent variable is influenced

9. Lecture 6 – Measurement Cont’d A variable may be continuous or discrete Continuous Age, height, time Discrete Gender, book type

10. Lecture 6 – Measurement Cont’d There are four categories or scales of measurement. These are: –nominal –ordinal –interval scale –ratio scale

11. Lecture 6 – Measurement Cont’d Nominal –lowest scale –limits data to categories only –no indication of rank or value e.g. gender, colour

12. Lecture 6 – Measurement Cont’d

13. Ordinal –limits data to categories –indicates order –interval has no meaning e.g. place in a race (first, second, third) skill level (unskilled, semi-skilled and skilled)

14. Lecture 6 – Measurement Cont’d

15. Interval Scale –limits data to categories –indicates order –interval has meaning –No true zero e.g. Celcius scale, IQ, Rating scale

16. Lecture 6 – Measurement Cont’d

17. Ratio Scale –limits data to categories –indicates order –interval has meaning –true zero e.g. age, length

18. Lecture 6 – Measurement Cont’d

19. Validity –accuracy of measurement Reliability –repeatability of measurement

20. Lecture 6 – Measurement Cont’d Validity –Internal (isolation of factors) –External (sampling) Reliability –Internal (instrument, observers) –External (repeatability by other researchers) (clear and detailed methodology)

21. Lecture 6 – Measurement Cont’d A researcher conducts an experiment to compare the durability of a new construction method with that of the traditional construction method. A one-mile strip of road in a remote area of Manchester is selected and divided into two sections. Construction following one design is done in one section while construction following the other design is done in the other section. Weekly inspections are made and measurements taken of deterioration of the surface. Two assistants work on the project. One collects data from one section while the other collects data from the other section.

22. Lecture 6 – Measurement Cont’d Accurate, Precise Valid, Reliable

23. Lecture 6 – Measurement Cont’d Inaccurate, Precise Invalid, Reliable

24. Lecture 6 – Measurement Cont’d Inaccurate, Imprecise Invalid, unreliable