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Comparison of Groups at Baseline

Richard Chambers

Independent samples t-tests were performed to detect significant preintervention (Time 1, before the 10-day meditation course) differences between meditators' and nonmeditators' raw baseline scores on the BDI, BAI, PANAS, RRS, MAAS, and DSB. All indices were examined for missing values and to ensure they satisfied the assumptions for t-test (Gravetter & Wallnau, 2000). No missing values were found, and the assumptions of homogeneity of variance, normality, and independence of observations were upheld.

There was a significant between-group difference in participants' scores on the BDI and MAAS at preintervention, with the meditators (i.e., those about to undergo the intervention) scoring significantly higher than the controls on both indices. Baseline scores on the BAI, PANAS (positive and negative dimensions), RRS and DSB were all nonsignificantly different across the two groups (Table 2).

There were some between-group differences in participants' measures of affect and executive function prior to the intervention.

Table 2

Means, Standard Deviations and Between-Groups t-test Statistics for Variable Scores across Groups at T1


Meditators (n = 20) Nonmeditators (n = 20)

Measure Mean SD Mean SD t d
BDI 8.05 5.12 4.6 3.98 2.38* .76
BAI 8.40 7.30 5.15 5.43 1.60 .51
PANAS+ 31.90 5.99 31.20 11.12 .25 .08
PANAS - 13.25 3.11 11.80 3.47 1.39 .45
RRS 48.50 12.77 46.05 14.28 .57 .18
MAAS 54.35 14.27 63.20 10.32 -2.25* -.72
DBS 8.05 2.58 8.35 2.41 -.38 -.12

* p < .05 (2-tailed); BDI = Beck Depression Inventory; BAI = Beck Anxiety Inventory; PANAS = Positive and Negative Affect Scale (+ and - refer to the positive and negative affect dimensions, respectively); RRS = Ruminative Responses Scale; MAAS = Mindful Awareness Attention Scale; DBS = Digit Span Backwards subscale of the Wechsler Adult Intelligence Scale, 3rd Edition (WAIS III).

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