6 Evidence Appraisal: Research 105
Research Design Distinctive Features Examples
Nonexperimental
(quantitative)
■■May have an
intervention
■■No random assignment
to group(s)
■■No control group
■■Descriptive
■■Predictive
■■Explanatory
■■Time-dimensional
Qualitative ■■No randomization
■■No manipulation
■■Little control of the
natural environment
■■Basic qualitative descriptive
■■Ethnography
■■Grounded theory
■■Phenomenology
■■Narrative inquiry
■■Case study
Mixed methods ■■Includes both
quantitative and
qualitative elements
■■Combination of
quantitative and
qualitative elements
may provide more than
either by itself
■■Convergent parallel
■■Explanatory sequential
■■Exploratory sequential
■■Multiphasic
Experimental Studies
Experimental studies, or RCTs, use the traditional scientific method. The inves-
tigator obtains verifiable, objective, research-based knowledge by observing or
measuring in a manner such that resulting evidence is reproducible. Types of
experimental designs that an EBP team may encounter include pretest–posttest
control group (the original, most widely used experimental design); posttest only;
randomized block; wait-list control group (delay of intervention design); and
crossover/repeated measures (Polit & Beck, 2017).
