3 Data Types and Data Structures Free Online FlashCards

How do a variable’s meaning and representation differ?

Meaning describes what a variable represents, such as a category or quantity; representation describes how it is stored, such as an integer or string.

What is a discrete quantitative variable?

A discrete quantitative variable takes countable values, such as the number of visits.

What defines a binary variable?

A binary variable has two possible categories, often represented as True/False or 0/1. Numeric coding alone does not make it a measurement.

What comparisons does a nominal scale support?

A nominal scale distinguishes categories with no inherent order. Useful summaries include counts, proportions, and the most common category.

How is a table organized in a common tidy format?

In a common tidy format, each column represents a variable, each row an observation, and each table one kind of observational unit.

How do you count students when each student has multiple result rows?

If each row is a student-course result, counting rows counts results, not students. Count distinct student IDs to count students.

How are repeated measurements arranged in long format?

In long format, repeated measurements appear on separate rows, often making grouping or plotting by category convenient.

Why isn’t a numeric postal code necessarily quantitative?

A postal code is a label, even if stored as an integer. Arithmetic such as averaging postal codes has no useful meaning.

What is a continuous quantitative variable?

A continuous quantitative variable can vary along a continuum, as a measured quantity such as height can.

What distinguishes an ordinal scale?

An ordinal scale has ordered categories, but the spacing between ranks is not established as equal. A median or rank comparison may be useful.

What can an interval scale tell you, and what can’t it justify?

An interval scale has ordered values with equal intervals but no absolute zero. Differences can be meaningful, but ratios are not; 20°C is not twice as warm as 10°C.

What makes a measurement scale a ratio scale?

A ratio scale has equal intervals and a meaningful zero, so differences and ratios are meaningful.