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Statistical Models

Introduction​

OpenStats currently supports two types of statistical models: linear models and generalized linear models.

In this section, we demonstrate how to construct a simple statistical model using the CO2 dataset.
The question of interest is how the CO2 uptake of plants depends on the atmospheric CO2 concentration.
Additionally, we investigate differences between chilled and non-chilled plants.

Each statistical model is defined using the Formula Editor, which can be opened via the dedicated button in the top-left corner.

First, select the dependent variable (response), here CO2 uptake, using the dropdown menu that lists all columns of the dataset.

Next, define the predictors using the buttons on the right-hand side.
In this example, we construct the term: conc * Treatment

This specifies:

  • the main effect of conc
  • the main effect of Treatment
  • and their interaction

If you only want to include the main effects without the interaction, you can use: conc + Treatment

For more details, refer to the question mark buttons available in each tab of OpenStats.

Tables

Model visualization​

For each statistical model a plot is created which visualizes the prediction and the uncertainty. The plot below shows the relationship between CO2 concentration (conc) and the predicted CO2 uptake of plants.

Two groups are displayed:

  • Chilled plants (red)
  • Non-chilled plants (blue)

Several key patterns can be observed:

  • Increasing trend:
    For both groups, CO2 uptake increases as the concentration increases.

  • Group differences:
    Non-chilled plants show consistently higher uptake compared to chilled plants across all concentration levels.

  • Interaction effect:
    The difference between the two groups changes slightly with increasing concentration, indicating that the effect of CO2 concentration depends on the treatment.

  • Uncertainty bands:
    The shaded areas around the lines represent variability in the predicted values. Wider bands indicate greater uncertainty.

Overall, the plot provides an intuitive understanding of how CO2 concentration and treatment jointly influence plant uptake.

Tables