Time-Dependent Cox
Time-Dependent Cox is one of the statistical analyses applied automatically in MerQur. This page illustrates — on a Health Sciences sample dataset — how the analysis is run, what the MerQur output looks like, and how the result is reported in APA 7 format.
🎯 What is it for?
Time-Dependent Cox automatically performs all assumption checks required for the data type (normality, homogeneity of variance, etc.) in the background and presents the results in a clear table + chart. Automatic APA 7-formatted interpretation, effect sizes (Cohen’s d, η², R²) and 95% confidence intervals are reported.
📌 When is it used?
- Statistical analysis of measurements in the Health Sciences domain
- To produce APA 7-compatible result tables for academic publications
- Hypothesis testing and decision-making processes
- Undergraduate / master’s / PhD theses after the appropriate method has been selected
📐 Assumptions
- Appropriate scale — Variables must be at the measurement level required by the analysis (nominal/ordinal/interval/ratio)
- Independent observations — Observations must come from individuals independent of one another
- Sufficient sample size — The minimum n requirement for the analysis must be met
- Outlier check — Outliers must be detected and evaluated
If assumptions are violated, MerQur automatically suggests a non-parametric or robust alternative.
🛠 How to do it in MerQur
Load the data. Select the sample file from File → Open. MerQur auto-detects column types.
Select the analysis. From the left side select Time-Dependent Cox.
Panel assignments (form fields in the program):
- Birey ID:
hasta_id - Baslangic:
baslangic - Bitis:
bitis - Olay sutunu (0/1):
olay - Kovaryans(lar):
['HbA1c'] - Penalizer:
0.0
Optional settings. Effect size ✓ · 95% confidence interval ✓ · Assumption checks (automatic).
▶ Run — click the button. Results are produced automatically as a table + chart.
📄 Export to Word. APA 7-formatted report with italic statistical symbols.
📊 Sample Dataset — Health Sciences
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 Health Sciences:
Tip/90_tvcox_HbA1c_death.xlsx
🎬 Scenario
We build a Cox model where the predictor (HbA1c) changes over time. For a time-varying covariate, time-dependent Cox is appropriate.
⚙️ Variable Selection
- Unit (id): patient_id
- Start: start
- Stop: end
- Event: event
- Predictor(s): HbA1c
Data Preview (First 5 Rows)
| patient_id | start | end | HbA1c | event |
|---|---|---|---|---|
| 1.0 | 0.0 | 3.0 | 7.49 | 0.0 |
| 1.0 | 3.0 | 6.0 | 7.71 | 0.0 |
| 1.0 | 6.0 | 9.0 | 7.41 | 0.0 |
| 1.0 | 9.0 | 12.0 | 7.17 | 0.0 |
| 1.0 | 12.0 | 15.0 | 7.35 | 0.0 |
n = 871 · Columns: patient_id, start, end, HbA1c, event
📈 MerQur Output
💬 Interpretation
We built a Cox model where the predictor (HbA1c) CHANGES over time: for each patient the current HbA1c value was used via start-stop intervals; the effect here is non-significant (HR = 1.096, p = 0.58). Time-dependent Cox correctly handles non-constant covariates (changing HbA1c, changing clinical status) — it uses the predictor’s current value at the event time. In medicine it is the right method for modeling the effect of time-varying clinical values (labs, treatment) on an event.
⚠ Common Mistakes
- Misidentifying the data type (e.g., loading a categorical variable as numeric)
- Skipping assumption checks and going straight to the p-value
- Failing to report effect size — APA 7 requires both p and effect size
- Failing to apply a Type I error correction (Bonferroni/Tukey) in multiple comparisons
- Not switching to a non-parametric alternative when n is insufficient
📹 Video Walkthrough
Watch the video below for an end-to-end walkthrough of this analysis on a Health Sciences file.
▶ Time-Dependent Cox — video walkthrough
A complete end-to-end walkthrough of this analysis in MerQur, narrated on screen. Narration is in Turkish.
🎓 Education Sciences · 🧪 Natural Sciences & Mathematics · 🏛 Architecture, Planning & Design · ⚙ Engineering · 📊 Social, Humanities & Admin Sciences · 🏃 Sport Sciences · 🌾 Agriculture, Forestry & Aquatic
📚 If You Used This Analysis, Cite MerQur
If you performed this analysis using MerQur in a scientific study, please use the citation below as part of your academic citation obligations (APA 7):
Örücü, Ö. K. (2026). MerQur: Integrated Academic Data Analysis & Reporting Platform [Computer software] (Version 1.0.0). https://doi.org/10.53463/merqur.2026001
For BibTeX, RIS, EndNote and the English citation form: all citation formats →
- American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.).
- Field, A. (2018). Discovering statistics using IBM SPSS Statistics (5th ed.). Sage.
- Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Lawrence Erlbaum.