Understanding Tableau Concepts15% of the exam
Dimensions and measures in the Data pane
What dimensions (qualitative fields that group the data) and measures (quantitative fields that get aggregated) contain, how Tableau assigns each role when it connects, how to read the role from a pill, and how to convert a misclassified number into a dimension.
Understand dimensions and measures: Explain what kind of information dimensions usually contain; Explain what kind of information measures usually contain; Explain the difference between dimensions and measures.
~7 min read · 8 practice questions ·
What the exam expects
- Recognize which fields of a data source usually become dimensions: qualitative values such as names, dates and geographic data.
- Recognize which fields usually become measures: numeric, quantitative values that can be added, averaged or otherwise aggregated.
- Explain the difference: dimensions group or segment the data and set the level of detail; measures are aggregated within those groups.
- Predict how Tableau assigns a role when it connects, including numeric fields named with ID or Key, and fix a misclassified field with Convert to Dimension.
- Read a pill on a shelf and tell whether the field is used as a dimension or a measure.
Key terms:
- Dimension: a field that groups or segments the data; Tableau doesn't aggregate it.
- Measure: a field of numeric values that Tableau aggregates when you drag it into the view.
- Aggregation: a function such as SUM or AVG that turns many row values into one value per mark.
- Level of detail: how granular the view is, set by the dimensions in it.
Key facts
Dimension contents
- Detail
- Qualitative values such as names, dates or geographical data
Measure contents
- Detail
- Numeric, quantitative values that you can measure
Measure dragged into the view
- Detail
- Tableau applies an aggregation, shown before the name
Default role, relational source
- Detail
- Text, date and Boolean fields are dimensions; numeric fields are measures
Numeric fields named with ID or Key
- Detail
- Categorized as dimensions even when numeric
Data pane gray line
- Detail
- Dimensions above it, measures below it, per table or folder
Convert in the Data pane
- Detail
- Affects all future uses of the field in the workbook
Dimensions in the query
- Detail
- Expressed as GROUP BY clauses; not aggregated
Measure set to Discrete
- Detail
- Shows headers but is still a measure and still aggregated
Sources for this section (4)
- When are all the fields in a view dimensions, even a numeric one?
- Why can't a Customer Name dimension be made continuous?
- Why can't a pill's missing aggregation function be trusted on a cube data source?
- Which aggregations can make a dimension pill effectively a measure?
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