Table 7 Robustness checks Certification... | Emerald Publishing

Table 7

Robustness checks

Certification event study
Period	AP median	AP mean	Normality	Skewness	p-value (WSR)	p-value (sign test)
Workforce score (decertified firms – Group 2)
t − 2 to t − 1	−0.48	−0.92	No		0.426	0.524
t − 1 to t	1.34	2.14	No		0.151	0.233
t − 1 to t + 1	3.40	5.03	No	X	0.033*	0.028*
t − 1 to t + 2	5.25	6.87	No	X	0.012*	0.017*
t − 1 to t + 3	6.11	7.95	No		0.003**	0.010*
t − 1 to t + 4	6.62	8.43	No		0.002**	0.003**
t − 1 to t + 5	7.04	8.80	No		0.002**	0.002**
Workforce score (certified firms – Group 1)
t − 2 to t − 1	−0.21	−1.45	No	X	0.541	0.647
t − 1 to t	2.47	3.52	No	X	0.089	0.158
t − 1 to t + 1	4.36	6.24	No		0.016*	0.023*
t − 1 to t + 2	5.68	7.33	No	X	0.007**	0.009**
t − 1 to t + 3	7.20	8.49	No		0.001**	0.003**
t − 1 to t + 4	8.85	9.90	No		0.000***	0.001**
t − 1 to t + 5	10.18	11.32	No	X	0.000***	0.000***

Certification event study
Period	AP median	AP mean	Normality	Skewness	p-value (WSR)	p-value (sign test)
Workforce score (decertified firms – Group 2)
t − 2 to t − 1	−0.48	−0.92	No		0.426	0.524
t − 1 to t	1.34	2.14	No		0.151	0.233
t − 1 to t + 1	3.40	5.03	No	X	0.033*	0.028*
t − 1 to t + 2	5.25	6.87	No	X	0.012*	0.017*
t − 1 to t + 3	6.11	7.95	No		0.003**	0.010*
t − 1 to t + 4	6.62	8.43	No		0.002**	0.003**
t − 1 to t + 5	7.04	8.80	No		0.002**	0.002**
Workforce score (certified firms – Group 1)
t − 2 to t − 1	−0.21	−1.45	No	X	0.541	0.647
t − 1 to t	2.47	3.52	No	X	0.089	0.158
t − 1 to t + 1	4.36	6.24	No		0.016*	0.023*
t − 1 to t + 2	5.68	7.33	No	X	0.007**	0.009**
t − 1 to t + 3	7.20	8.49	No		0.001**	0.003**
t − 1 to t + 4	8.85	9.90	No		0.000***	0.001**
t − 1 to t + 5	10.18	11.32	No	X	0.000***	0.000***

Decertification event study
Period	AP median	AP mean	Normality	Skewness	p-value (WSR)	p-value (sign test)
Workforce score (decertified firms – Group 2)
t − 2 to t − 1	1.24	1.53	No		0.188	0.265
t − 1 to t	0.19	−0.36	No		0.714	0.798
t − 1 to t + 1	−2.67	−3.71	No		0.062	0.079
t − 1 to t + 2	−5.45	−6.68	No		0.008**	0.011*

Decertification event study
Period	AP median	AP mean	Normality	Skewness	p-value (WSR)	p-value (sign test)
Workforce score (decertified firms – Group 2)
t − 2 to t − 1	1.24	1.53	No		0.188	0.265
t − 1 to t	0.19	−0.36	No		0.714	0.798
t − 1 to t + 1	−2.67	−3.71	No		0.062	0.079
t − 1 to t + 2	−5.45	−6.68	No		0.008**	0.011*

Note(s): *, ** and *** Significant at 5, 1 and 0.1% levels, respectively (Benjamini-Hochberg's (1995) false discovery rate correction)