Paired Samples t-Test
Paired Samples t-Test is one of the statistical analyses applied automatically in MerQur. This page illustrates — on a Agriculture, Forestry & Aquatic 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?
The Paired Samples t-Test automatically performs all required assumption checks (normality, homogeneity of variance, etc.) for the relevant data type in the background and presents the results with a clear table + chart. Automatic interpretation in the APA 7 standard, effect sizes such as Cohen’s d/η²/R², and 95% confidence intervals are reported.
📌 When is it used?
- Statistical analysis of measurements in the Agriculture, Forestry & Aquatic 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 Paired Samples t-Test.
Panel assignments (form fields in the program):
- Column 1:
dbh_oncesi_cm - Column 2:
dbh_sonrasi_cm
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 — Agriculture, Forestry & Aquatic
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 Agriculture, Forestry & Aquatic:
Ziraat_Orman_Su/05_paired_t_dbh_gubreleme.xlsx
🎬 Scenario
In a fertilization trial we track diameter growth on the same trees. For each tree we measured diameter before fertilization (dbh_before_cm) and after one growing season (dbh_post_cm). Since the measurements come from the same individuals at two time points, the groups are dependent. The paired t-test is the correct choice: did fertilization raise per-tree diameter growth by a statistically significant amount?
⚙️ Variable Selection
- Measurement 1 (before): dbh_before_cm
- Measurement 2 (after): dbh_post_cm
- >> ADVANCED PARAMETERS (optional in the form — what they do):
- Hypothesis direction (two-sided / right / left).
- Effect sizes: Hedges g; d_av (standardized by the average SD).
- Effect-size CI; pairwise correlation between the two measures.
- Shapiro / K-S on the differences; descriptives; Bootstrap CI of the mean difference.
Data Preview (First 5 Rows)
| tree_id | dbh_before_cm | dbh_post_cm | type | experiment_year |
|---|---|---|---|---|
| 1 | 26.5 | 29.2 | black_pine | 2 |
| 2 | 21.9 | 24.2 | black_pine | 2 |
| 3 | 22.6 | 23.5 | black_pine | 2 |
| 4 | 25.5 | 29.3 | black_pine | 2 |
| 5 | 27.8 | 29.1 | black_pine | 2 |
n = 60 · Columns: tree_id, dbh_before_cm, dbh_post_cm, type, experiment_year
📈 MerQur Output
💬 Interpretation
Here we compared the same trees before and after fertilization — each tree is its own control. The result is striking: t(59) = -19.54, p far below one in a thousand. The negative sign shows the later measurement is larger than the earlier one, i.e. diameters increased. What is truly impressive is the effect size: Cohen’s d_z = -2.52, more than three times the “large” threshold of 0.8 — the effect of fertilization on diameter growth is not just significant, it is enormous. This is the power of a paired design: because we compare the same individuals before and after, we eliminate between-tree variability and see the pure effect of fertilization very clearly. In practice, the treatment strongly accelerated diameter growth. >> ADVANCED PARAMETERS (optional in the form — what they do): – Hypothesis direction (two-sided / right / left). – Effect sizes: Hedges g; d_av (standardized by the average SD). – Effect-size CI; pairwise correlation between the two measures. – Shapiro / K-S on the differences; descriptives; Bootstrap CI of the mean difference.
⚠ 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 Agriculture, Forestry & Aquatic file.
▶ Paired Samples t-Test — video walkthrough
This section is part of the Veriye İlk Bakış ve Parametrik Testler video (13 analyses in one video). The link below jumps straight to 9:09, where this analysis begins. Narration is in Turkish.
🎓 Education Sciences · 🧪 Natural Sciences & Mathematics · 🏛 Architecture, Planning & Design · ⚙ Engineering · 🏥 Health Sciences · 📊 Social, Humanities & Admin Sciences · 🏃 Sport Sciences
📚 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.