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. Author manuscript; available in PMC: 2013 Apr 17.
Published in final edited form as: Eur J Pain. 2012 Feb 17;16(7):983–993. doi: 10.1002/j.1532-2149.2011.00108.x

Table 1.

Simple mediation model representing case–control differences in mean ratings of hyperalgesia at 46 °C through self-reported sleep quality.

Effect Coefficient SE t Sig. 95% CI bias corrected
c 11.98 4.68 2.56 <0.05
a   1.32 0.46 2.86 <0.01
b   1.82 0.93 1.96 <0.05
c′   9.57 4.78 2.00 <0.05
a × b   2.34 1.51 d (LL = 0.23, UL = 6.52)

This shows unstandardized coefficients for the unconditional indirect effect of group differences in suprathreshold heat pain ratings through self-reported sleep quality.

a, IV to mediator; b, direct effect of mediator on DV; c, total effect of IV on DV through proposed mediator; c′, direct effect of IV on DV; a × b, indirect effect of IV on DV through proposed mediator; IV, independent variable (i.e. TMJD-control status); DV, dependent variable (i.e. hyperalgesia at 46 °C; LL, lower limit; UL, upper limit.

d

A p-value for the indirect effect is not provided because such a p-value is contingent upon a normal distribution of the indirect effect. Given that the product of the a and b path coefficients is always positively skewed, interpretation of this p-value can be misleading.