Raymond Martin

rmartin@utech.edu.jm

Lecture 6 – Measurement

Data are: – pieces of observable information – limited by measurement

Measurement is:– limiting the data

          

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

          

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.         

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.        

Lecture 6 – Measurement Cont’d

Identify the constants and the variables

Lecture 6 – Measurement Cont’d

An Independent variable influences while a Dependent variable is influenced

Lecture 6 – Measurement Cont’d

A variable may be continuous or discrete

Continuous

• Age, height, time

Discrete

• Gender, book type

Lecture 6 – Measurement Cont’d

There are four categories or scales of measurement. These are:– nominal– ordinal– interval scale– ratio scale

Lecture 6 – Measurement Cont’d

Nominal– lowest scale – limits data to categories only– no indication of rank or value

e.g. gender, colour

Lecture 6 – Measurement Cont’d

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Black White Brown Purple

Lecture 6 – Measurement Cont’d

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)

Lecture 6 – Measurement Cont’d

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1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Lecture 6 – Measurement Cont’d

Interval Scale– limits data to categories – indicates order – interval has meaning– No true zero

e.g. Celcius scale, IQ, Rating scale

Lecture 6 – Measurement Cont’d

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Temperature

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Lecture 6 – Measurement Cont’d

Ratio Scale– limits data to categories – indicates order – interval has meaning– true zero

e.g. age, length

Lecture 6 – Measurement Cont’d

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Age

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ght

Lecture 6 – Measurement Cont’d

Validity– accuracy of measurement

Reliability– repeatability of measurement

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)

Lecture 6 – Measurement Cont’dA 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.

 

Lecture 6 – Measurement Cont’d

Accurate, Precise Valid, Reliable

Lecture 6 – Measurement Cont’d

Inaccurate, Precise

Invalid, Reliable

Lecture 6 – Measurement Cont’d

Inaccurate, Imprecise

Invalid, unreliable