Unit 1Section 1-3

1-3: Variables and Types of Data

Variables can be classified in two ways:

Qualitative Variable– variables that can be placed into distinct categories, according to some characteristic or attribute.

Quantitative Variable– variables that are numerical and can be ordered or ranked.

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Quantitative Variables

There are two types of quantitative variables:

Discrete Variables – can be assigned values such as 0, 1, 2, 3. Variables are able to be counted.

Continuous Variables – can assume an infinite number of values between any two specific values. Values are obtained by

measuring (often include decimals and fractions).

The classification of variables can be summarized as follows:

Section 1-3

Data

Qualitative

Quantitative

Discrete Continuous

Boundaries– ranges of values that could have been rounded to the recoded value.

For Example: If you are measuring foot length to the nearest centimeter, then a value of 31cm could be any thing between 30.5 and 31.5 (not including 31.5).

Measurement Scales– how variables are categorized, counted, or measured. There are four main types of scales: nominal, ordinal, interval, and ratio.

Section 1-3

Measurement Scales

Nominal – classifies data into mutually exclusive (non-overlapping), exhausting categories in which no order or ranking can be imposed on the data.

Examples: eye color, political party, zip code

Ordinal – classifies data into categories that can be ranked; however, precise differences between the ranks do not exist.

Examples: letter grades, Olympic medals

Interval – classifies data into categories that can be ranked and have precise differences. However, there is no meaningful zero (a reading of zero doesn’t mean that it does not exist).

Examples: temperature, SAT scores

Ratio - possesses all the characteristics of interval measurement and there exists a true zero.

Examples: height, weight, time

Section 1-3

Complete 1-2 & 1-3 Worksheet

Homework