Table 2. Data quality and deleted cases, percentages by mode.

ESPAD®Italy 2015 Comparison study (P&P vs computerized administration mode)		P&P	Computerized	Pearson	p-value
		N = 811	N = 862	chi2 (df)
Cases with missing on gender (%)		1.7	4.9	12.8 (1)	0.00
Cases with less than 50% of the core questions answered (%)		0.5	7.2	49.5 (1)	0.00
Cases with repetitive extreme response patterns (%)		1.2	2.9	5.7 (1)	0.02
Total deleted cases	N	27.0	91.0
	%	3.3	10.6	33.3 (1)	0.00
Valid cases		784	771