Crossed LMM (Crossed Random Mixed Model)
v1.0.1
Natural Sciences & Mathematics context — the two random factors are NOT nested but crossed. olcum ~ 1 + (1|cihaz) + (1|numune). Each cihaz is paired with all numunes.
🎯 What is it for?
Different from the classical nested structure: each device pairs independently with different samples (not every sample under every device; crossed). In Natural Sciences & Mathematics, it estimates the random variance of the two factors separately.
📌 When is it used?
- Rater × ratee (each rater evaluates every sample)
- Operator × device (each operator uses every device)
- Measurement design with two random effects
⚙ Assumptions
- The two random factors are independent of each other (not nested).
- ≥1 observation in each (cihaz, numune) cell (empty cells bias the estimates).
- Random effects ~ Normal(0, σ²).
📊 How to Run It in MerQur?
Panel assignments (form fields in the program):
- Dependent Variable:
deger - Factor A:
faktor_a - Factor B:
faktor_b - A Type:
random - B Type:
random - SS Type:
1
📊 Sample Dataset — Natural Sciences & Mathematics
ℹ Note: The scenario, MerQur output and interpretation below were produced by actually running the real example dataset in MerQur. Numeric results on your own data will differ; the goal is to show how the analysis is set up and interpreted end-to-end.
🎬 Example File
This analysis is demonstrated on the following example dataset for Natural Sciences & Mathematics:
Fen_Matematik/109_crossed_lmm_A_B.xlsx
🎬 Scenario
We model a design where two random factors are crossed. For two independent
classification axes, crossed LMM is appropriate.
⚙️ Variable Selection
- Dependent variable: value
- Factor (categorical): factor_a
- 2nd Factor: factor_b
Data Preview (First 5 Rows)
| factor_a | factor_b | value |
|---|---|---|
| A1 | B1 | 53.8 |
| A1 | B1 | 55.31 |
| A1 | B1 | 50.68 |
| A1 | B1 | 55.81 |
| A1 | B1 | 56.05 |
n = 128 · Columns: factor_a, factor_b, value
📈 MerQur Output
─────────────────────────────────────────────
A x B interaction: F = 14.67, p < .001 *** main effects ns (A: p=0.767, B: p=0.480) outcome: value
💬 Interpretation
We modeled a design where two random factors are crossed rather than nested (each level of A pairs with each level
of B): while the main effects are non-significant (A: p=0.77, B: p=0.48), the A x B interaction is very strong
(F = 14.67, p < .001) — so the effect depends on the COMBINATION of factors. Crossed LMM, unlike nested, handles
two independent grouping axes (e.g. method x batch, each method in each batch) at once. In the lab it is the right
choice for jointly analyzing the effects and interaction of two independent classification axes.
⚠ Common Mistakes
- Specifying a crossed structure when the design is actually nested — make sure each (device, sample) pair is genuinely independent.
- A very sparse matrix (many empty cells in device×sample) — the model cannot be fit or is unstable.
- If the device-ICC is low and the sample-ICC is high, shrinkage is tighter in estimating the sample.
📚 MerQur’a Atıf
Örücü, Ö. K. (2026). MerQur: Integrated Academic Data Analysis & Reporting Platform [Computer software] (Version 1.0.0). https://doi.org/10.53463/merqur.2026001
📝 Üretim Notu — Bu sayfadaki örnek veri sentetik olarak üretilmiştir (sabit SEED=42, generator: samples/Ileri_Duzey_v102/_generate_v102_datasets.py). Sayfa içeriği Anthropic Claude desteği ile hazırlanmış, akademik doğruluk yazar tarafından kontrol edilmiştir.