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SPSS Guide
How to Read SPSS Output — Independent t-test Step by Step
Learn to interpret Levene's test, t-statistic, df, p-value, mean difference, and 95% CI from a real SPSS Independent Samples Test table. Includes Cohen's d calculation and APA-7 write-up.
📊 t(48) = −3.42, p = .001, d = 0.68 | ابدأ بـ Levene
Step-by-step solution
💻 21 · How to Read SPSS Output — Independent t-test
Interpreting the SPSS Independent Samples Test Table
SPSS Guide
Research Question:
A researcher compared anxiety scores between cognitive therapy (n=25) and waitlist (n=25) groups. The SPSS output is shown below — how to read it?
| Levene's F | Sig. | t | df | Sig.(2-tail) | Mean Diff. | SE | 95% CI Lower | 95% CI Upper | |
|---|---|---|---|---|---|---|---|---|---|
| Equal var. assumed | 2.14 | .149 | −3.42 | 48 | .001 | −4.80 | 1.40 | −7.63 | −1.97 |
| Equal var. not assumed | −3.42 | 45.7 | .001 | −4.80 | 1.40 | −7.64 | −1.96 |
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1Step 1 — Check Levene's Test first: F = 2.14, Sig. = .149. Since .149 > .05 → variances are equal → use ROW 1 (Equal variances assumed).
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2Step 2 — Read t, df, and p: t = −3.42, df = 48, p = .001. Since p = .001 < .05 → significant difference exists.
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3Step 3 — Calculate Cohen's d (SPSS does not show it):$$d = \frac{|t|}{\sqrt{n_1 + n_2}} \times \sqrt{2} = \frac{3.42}{\sqrt{50}} \times \sqrt{2} = \frac{3.42}{7.07} \times 1.414 = 0.68 \quad (\text{large})$$
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4Step 4 — Interpret the 95% CI: The CI does not contain zero → confirms statistical significance. The therapy group scored 4.80 points lower in anxiety.
−3.42
t(48)
.001
p
−4.80
Mean Diff.
0.68
Cohen's d
🔴 Reject H₀ — Significant difference in anxiety scores, t(48) = −3.42, p = .001.
APA-7
An independent-samples t-test revealed a significant difference in anxiety scores between the cognitive therapy group (M = 18.20, SD = 7.10) and the waitlist group (M = 23.00, SD = 6.80), t(48) = −3.42, p = .001, d = 0.68, 95% CI [−7.63, −1.97].