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Group analysis (STUDY)

From one participant to a group: preparing files, creating a STUDY from files or BIDS, designing conditions, precomputing and plotting measures, statistics, and exporting results.

10 lessons: 6 core, 4 recommended

After this station you can:

  • Check that participant files are ready for a STUDY
  • Create a STUDY and define within- and between-subject designs
  • Compute and plot group ERPs and spectra
  • Test differences with multiple-comparison correction
  • Export values to a table for your stats software

Lessons

  1. What a STUDY is and when you need oneCore10 min
  2. Creating a STUDYCore15 minComing soon

    In this lesson you will: Create a STUDY from the D6 files with the Browse for datasets window and with a script.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

  3. Creating a STUDY from BIDSRecommended12 minComing soon

    In this lesson you will: Download a small part of ds002680 in BIDS format, and describe what each file holds.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

  4. STUDY designs & variablesCore15 min
  5. Precomputing measuresCore15 min
  6. Plotting group channel measuresCore15 minComing soon

    In this lesson you will: Plot the group ERP at a channel for each cell of the design with Study > Plot channel measures.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

  7. Statistics & multiple comparisonsCore15 minComing soon

    In this lesson you will: Run a paired test of the two picture types at Pz with the STATS button, and mark the significant times with FDR correction.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

  8. Exporting results for papers & stats softwareRecommended12 min
  9. IC clusteringRecommended15 minComing soon

    In this lesson you will: Select the components to cluster by dipole residual variance with Study > Edit study info.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

  10. LIMO EEGRecommended15 minComing soon

    In this lesson you will: Install the LIMO plugin and find its menus in EEGLAB.

    Read about it now in the official docs (opens in a new tab)

    This lesson is being written.

Test yourself

4 questions. Your score stays with you and isn't sent anywhere.

1. Before creating a STUDY, which of these must match across the participants' files? (Select all that apply)
Show the answer

The correct answer: The sampling rate, The epoch window and its number of points, Channel names in the same naming system, Event and condition names spelled the same way

A STUDY neither merges nor processes the data; it trusts that the files match, so a different rate or window makes functions crash or silently go wrong. The number of epochs naturally differs between people, but note it for each participant, because an average of few epochs is weak.

Review the lesson: What a STUDY is and when you need one

2. In D6 each participant has one gender (F or M), and every participant saw both animal and other pictures. How do you treat the gender variable?
Show the answer

The correct answer: A between-subject variable, stored in group, tested unpaired

A condition changes within a participant, and a group changes between participants. Gender is one value per participant, so it is between subjects and compares two groups of different people (unpaired). If you typed it as a condition, EEGLAB would treat it as within subjects, and the paired line would reveal it.

Review the lesson: STUDY designs & variables

3. Why do you write 'interp', 'on' explicitly when you call std_precomp from a script?
Show the answer

The correct answer: Because its script default is off while the window has it ticked, so you interpolate missing channels as the GUI does

Spherical interpolation of missing channels is ticked by default in the window, but interp defaults to off in a script. If all files have the same channels it changes nothing, and it is better to interpolate in each participant's file before the STUDY, where you can see it. Saving single trials (savetrials) is always on in current EEGLAB.

Review the lesson: Precomputing measures

4. Put the steps of a group analysis in a STUDY in order:
  1. Plot and test with a multiple-comparisons correction
  2. Check that the participants' files match
  3. Precompute the measures (ERP and spectrum)
  4. Create the STUDY and enter subject, condition and group for each file
Show the answer

The correct answer: 1. Check that the participants' files match, 2. Create the STUDY and enter subject, condition and group for each file, 3. Precompute the measures (ERP and spectrum), 4. Plot and test with a multiple-comparisons correction

Checking comes before creating, because a STUDY is created without error even if the files differ. Precomputing saves the measures that plotting and statistics read, and you can define or change designs before or after it.

Review the lesson: What a STUDY is and when you need one