Overview
This lecture explains how to set variable types and value labels in JASP with raw data, detailing categorical and continuous variables, and the importance of correct measurement levels.
Opening and Inspecting Raw Data
- Open raw data in JASP via Main Menu → Open → Data Library, choosing datasets without the JASP logo.
- Each column in the dataset has a name and an icon indicating its measurement level.
Types of Variables in JASP
- Three categorical variable types: nominal (numbers for groups), nominal text (text for categories), and ordinal (ordered categories).
- Nominal variables use group codes like 0 and 1 for categories such as control and experimental.
- Nominal text variables store categories as text (e.g., M/F for gender); SPSS calls these string variables.
- Ordinal variables have a meaningful order (e.g., mild/moderate/severe) and are indicated by three bars.
Continuous Variables and Changing Variable Types
- Continuous variables (scale data) are shown by a yellow ruler and usually contain decimals.
- Measurement levels can be manually changed by clicking the icon next to the variable name.
- Changing a numeric identifier (e.g., V1) from scale to nominal allows it to be used as a categorical variable.
- Changing nominal to scale removes value labels; caution is advised.
- Some variable types, like nominal text, cannot be changed to other types.
Setting Value Labels and Reordering
- Value labels provide meaningful names to group codes in categorical variables.
- Edit value labels by double-clicking the label, typing the new name, and pressing Enter.
- Reorder value labels using arrow buttons or quickly reverse the sequence with the reverse arrow icon.
Importance of Setting Variable Types
- Setting correct levels assists with variable selection in statistical tests and guides correct analysis placement.
- Reviewing and assigning levels familiarizes you with the data and supports best practices in data cleaning.
- Correct levels enable JASP to automatically choose the optimal display method for each variable type.
Key Terms & Definitions
- Nominal variable — categorical variable with group codes (no order).
- Nominal text variable — categorical variable with text-based categories.
- Ordinal variable — categorical variable with a meaningful order.
- Continuous variable (scale) — numeric variable with a continuous range, often with decimals.
- Value label — descriptive name assigned to coded values in categorical variables.
- Level of measurement — type of data: nominal, ordinal, or scale (continuous).
Action Items / Next Steps
- Practice opening a raw CSV in JASP and setting variable types and value labels.
- Explore changing variable types and reordering value labels in a dataset.
- Prepare to work with a more meaningful dataset in the next session.