Table 3.

Levels of Evidence, Definitions, and Frequency by the American Nurses Association-Recognized Standardized Nursing Terminologies^*

Level of Evidence	Definition	NANDA-I+	NOC+	NIC+	NNN+	ICNP	Omaha	CCC/ HHCC	PNDS	Combo
I. a. Systematic review of Randomized Clinical Trials	Integrated findings from multiple Randomized Clinical Trial studies using rigorous methods.	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0
I. b. Systematic review of non-Randomized Clinical Trials	Findings from multiple non-randomized trials using rigorous methods.	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0
II. a. Single Randomized Clinical Trial	Study that involve an intervention, randomization, and control of an independent variable.	2 (1)	1 (0)	1 (0)	1 (1)	0 (0)	0 (0)	0 (0)	0 (0)	0
II. b. Single Non-Randomized Clinical Trial	Quasi-experimental study with intervention but lacks randomization.	4 (1)	3 (0)	4 (1)	3 (3)	0 (0)	0 (0)	0 (0)	0 (0)	0
II. c. Single Non-Randomized Clinical Trial w/o control	As II. B, but also lacks control.	10 (6)	4 (0)	6 (1)	5 (5)	0 (0)	7 (7)	1 (1)	0 (0)	0
III. Systematic review of non-randomized studies	Integrated findings from multiple non-randomized intervention studies using rigorous methods	1 (1)	1 (1)	0 (0)	0 (0)	0 (0)	1 (1)	0 (0)	1 (1)	0
IV. Single correlational	Studies that explore the interrelationships among variables of interest without researcher intervention.	29 (23)	12 (9)	12 (7)	5 (5)	2 (1)	9 (8)	1 (0)	0 (0)	2
V. Systematic review of descriptive or qualitative studies	Systematic review of the multiple descriptive or qualitative Systematic review for development of new term	3 (1)	2 (0)	3 (1)	2 (1)	2 (1)	1 (0)	1 (0)	0 (0)	1
VI. Single descriptive or qualitative	Study focus to observe, describe and document aspects of a phenomenon as it naturally occurs without control of an independent variable.	120 (74)	38 (15)	73 (35)	38 (33)	29 (20)	25 (14)	14 (4)	8 (4)	22
Total*		169 (107)	61 (25)	99 (45)	54 (48)	33 (22)	43 (30)	17 (5)	9 (5)	25

^*The total outside the parentheses exceeds 312 because articles covering multiple standardized nursing terminology sets are counted multiple times; the total number inside the parentheses represents the number of articles exclusive to the designated standardized nursing terminology and across the standardized nursing terminology sets is equal to 312; + represents one standardized nursing terminology set, but listed separately because each component of the set (NANDA-I, NIC, NOC) can be studied by itself; NNN refers to NANDA-I, NOC, and NIC; Combo refers to studies that examine aspects of more than one standardized nursing terminology set.