Table 2

Missing-item rate, test–retest reliability and hospital-level reliability for patient-incident questions and incident index (n=10 514)

			Hospital-level reliability
	Missing item (%)	Test–retest reliability (n=163)	ICC	Reliability*	n For rel. 0.7†	n For rel. 0.8†	n For rel. 0.9†
Questions with five response categories (1, ‘not at all’ to 5, ‘to a very large extent’)
1. Do you believe you were incorrectly treated by the hospital in any way (as far as you yourself are able to judge)?	3.6	0.64	0.015	0.724	153	263	591
2. Did you get a wrong or delayed diagnosis in connection with your hospital stay?	25.0	0.72	0.024	0.760	95	163	366
3. Did you suffer any unnecessary injury or unnecessary problem as a result of a surgical procedure or examination?	30.7	0.56	0.020	0.704	117	198	446
4. Did you receive the wrong medication, or were you incorrectly medicated in any other way?	19.4	0.39	0.014	0.660	167	286	643
5. Did you experience insufficient hand hygiene (hand washing) among the staff?	15.8	0.54	0.014	0.673	164	282	634
6. If you experienced mistakes or unnecessary problems in connection with your hospital stay, did the staff handle the mistake or problem in a satisfactory way?	70.9	0.36	0.032	0.623	71	121	272
7. Did you experience that important information about you had reached the right people?	6.2	0.38	0.034	0.851	66	114	256
Questions with three response categories (1, ‘no’; 2, ‘once’; 3, ‘more than once’)
8. Did you experience any administrative mistakes during your hospital stay?	3.0	0.54	0.022	0.795	104	178	400
9. Did you experience that the staff forgot to check your identity?	2.7	0.51	0.009	0.604	263	451	1014
10. Did you experience that the staff forgot to give you important information?	3.1	0.16	0.014	0.709	164	282	634
Questions with two response categories
11. Did you get an infection in connection with your hospital stay? (1, ‘no’; 2, ‘yes’)	8.3	0.44	–	–	–	–	–
12. Was an updated list of your medications reviewed with you when you were discharged from hospital? (1, ‘yes’; 2, ‘no’)	26.0	0.67	–	–	–	–	–
13. When you were admitted, did you bring along an updated list of medications you were taking? (1, ‘yes’; 2, ‘no’)	43.6	0.61	–	–	–	–	–
Patient-incident index (range 0–12, sum of questions 1–12)	0.0	0.61	0.031	0.845	73	126	283

*Reliability refers to observed reliability given the sample size.
†n For rel. 0.7/0.8/0.9 indicates the sample size per hospital needed to obtain these three reliability levels.
ICC, intraclass correlation coefficient.