Info 2040Foundation of Quantitative

AnalysisWeek 2-1

Class Activities

• Think of a question that lead you to collecting a data set (comprising of data and cases)

• Eg. What types of telecommunication operators do students in info 2040 subscribed to? Or what are the weights of the students in this class?

• Create a data set (a minimum of 50 cases) in the Excel spreadsheet

• Arrange them as data and cases• You may find your data in the internet – describe

what the data is about, or for what purpose

Measurement

• The form in which our data represented• What do we normally measure?• How do we measure• What kind of measurements can you find

out there?• Why do we measure?• Most of the time we measure variables• What is a variable?

Measurement and Variable

• Measurement – the use of any rule to assign numbers to cases so as to represent the presence or absence or quantity of some attribute possessed by each case

• Variable – an attribute or characteristic that varies from one case to the next

Rules in Measuring

• Very important

• Depend on what is being measured

• More than one way to measure an attribute

• Sometimes called “scale” or “level” or measurement

• Will determine how we choose the statistical tools

Scale of Measurement

• Nominal

• Ordinal

• Interval

• Ratio

Nominal Scale• The lowest level of measurement• Describes in terms of quality of each case

– “what kind” NOT “how much”• Eg. Gender – male or female, • Describe presence or absence of an

attribute – eg. Yes or NO• When assigned numbers, the difference

has no mathematical value• How do we use statistics to describe data

in this category?

Ordinal Scale

• Involves assigning numbers to cases• Conveys quantitative information about

cases• Eg. Strongly agree = 1, Agree = 2,

Somewhat agree = 3, Disagree = 4, Strongly disagree = 5

• 1 is < 2, 3 is > 2• 2 – 1 ≠ 3 -2 (the different has no

mathematical value)

Interval Scale • Scores on the scale variable determined

by the number of fixed-sized units• No absolute 0 in the variable attribute• Arbitrary 0 point – 0 does not means

complete absence of attribute• 0 represents low quantity• The different can be mathematically

manipulated – 2 -1 = 3 – 2 = 1• What are other examples of variables

measured using interval scale?

Ratio Scale

• Highest, most flexible level of measurement

• Data available themselves to all of most powerful statistical procedures

• Similar to interval scale EXCEPT

• 0 means 0

• What are the example of variables measured using ratio scale?

Assignment 2

• In continuation with the data set earlier,

• Complete the data sheet with at least 50 cases and at least 4 variables that are measured with nominal, ordinal, interval, and ratio scale.