Ch. 10: The Nonexperimental and Quasi-Experimental Strategies Flashcards
similarity between the nonexperimental and quasi-experimental research strategies
involve comparisons of scores from different groups or different conditions
differences between the nonexperimental and quasi-experimental designs
- The nonexperimental design makes little or no attempt to minimize threats to internal validity
- The quasi-experimental design makes some attempt to minimize threats to internal validity and approaches the rigour of a true experiment
key elements of nonexperimental and quasi-experimental designs
- Often look like experiments in terms of their general structure
- Produces groups of scores to be compared for significant differences
- One variable is used to create the groups or conditions to be compared and the second is measured to obtain a set of scores within each condition
- Groups are defined in terms of a specific participant variable or in terms of time
two general categories of nonexperimental and quasi-experimental designs
- between-subjects (nonequivalent group designs)
- within-subjects (pre-post designs)
nonequivalent group design
a research study in which the different groups of participants are formed under circumstances that do not permit the researcher to control the assignment of individuals to groups, and the groups of participants are therefore, considered nonequivalent
is random assignment used in nonequivalent designs?
no, the researcher cannot use random assignment to create groups of participants
what is the main threat to internal validity in nonequivalent group designs
individual differences
Three common examples of nonequivalent group designs
- The differential research design
- The posttest-only nonequivalent control group design
- The pretest-posttest nonequivalent control group design
differential research design
a research study that compares preexisting groups
what type of research design is differential research?
nonexperimental nonequivalent group design
how do researchers assign participants to groups in the differential research design?
using participant characteristics
measurement of the dependent variable in the differential research design
A DV is then measured for each participant to obtain a set of scores within each group
goal of the differential research design
to determine whether the scores of one pre-existing group are consistently different from the scores of another pre-existing group
synonym for the differential research design
ex post facto research because it looks at differences after the fact
similarities between differential and correlational research
- A researcher simply observes two naturally occurring variables without any manipulation
- The results are interpreted in the same way
- Neither allows for a cause-and-effect explanation of a relationship
differences between differential and correlational research
- In differential research, the participant differences in one variable are used to create separate groups and the measurements of the second variable are made within each group. The researcher then compares the measurements for one group with the measurements from another
- In correlational research, the researcher treats all participants as a single group and simply measures the two variables for each individual
- They use different statistical analyses
nonequivalent control group design
uses preexisting groups, one of which serves in the treatment condition and the other in the control condition. The researcher does not randomly assign individuals to the groups
what type of research design is the nonequivalent control group design?
nonexperimental nonequivalent group design
posttest-only nonequivalent control group design
compares two nonequivalent groups of participants. One group is observed (measured) after receiving treatment, and the other group is measured at the same time but receives no treatment
what type of research design is the posttest-only nonequivalent control group design
nonexperimental nonequivalent group design
synonym for a posttest-only nonequivalent control group design
static group comparison
posttest-only nonequivalent control group design annotation
- Annotated using X and O, where X corresponds to the treatment and O corresponds to the observation or measurement
- A R is placed as the first symbol in each line of notation if the study used random assignment
what type of research design is the pretest-posttest nonequivalent control group design?
a quasi-experimental nonequivalent group design
pretest-posttest nonequivalent control group design
compares two non-equivalent groups. One group is measured twice, once before a treatment is administered, and once after. The other group is measured at the same two times but does not receive any treatment
annotation of pretest-posttest nonequivalent control group design
O X O (treatment group)
O O (nonequivalent control group)
benefits of the pretest-posttest nonequivalent control group design
- Allows researchers to determine whether the treatment or some other, time-related factor is responsible for the changes
- The addition of a pretest reduces threats to internal validity associated with individual differences
- Can provide some evidence to support a cause-and-effect relationship
what variables can become confounding in pretest-posttest nonequivalent control group designs?
time-related variables because groups are nonequivalent and often in separate locations
history effects
the influence of outside events
differential effects
when history effects differ from one group to another
pre-post designs
a research study in which a series of observations is made over time for one group of participants
goal of pre-post designs
to evaluate the influence of the intervening treatment or event by comparing the observations made before treatment with the observations made after treatment
what type of design are pre-post designs similar to?
the pretest-posttest nonequivalent control group design
differences between the pretest-posttest nonequivalent control group design and the pre-post designs
- pre-post designs have no control group
- the primary focus of its control group is to compare the treatment scores to the control group, not to compare the pretest scores with the posttest scores
threats to internal validity for pre-post designs
time-related factors
5 categories of time-related threats
- History
- Instrumentation
- Order effects
- Maturation
- Statistical regression
pre-post designs vs. within-subjects experimental designs
- Pre-post designs are similar to the within-subjects experimental design
- However, the within-subjects design uses counterbalancing to control time-related variables
- In a pre-post design, it is impossible to counterbalance the order of treatments
pretest-posttest design
each individual in a single group of participants is measured once before treatment and once after treatment
what type of research design is the pretest-posttest design?
a nonexperimental pre-post design
annotation of the pretest-posttest design
O X O
time-series design
has a series of observations for each participant before a treatment or event and a series of observations after the treatment or event
treatment
a manipulation administered by the researcher
event
an outside occurrence that is not controlled or manipulated by the researcher
what type of research design is the time-series design?
a quasi-experimental pre-post design
annotation of the time-series design
O O O X O O O
is the treatment manipulated by the researcher in a time-series design?
The intervening treatment/event (x) may or may not be manipulated by the researcher
interrupted time-series design
a study in which the intervening event is not manipulated by the researcher
applications of the time-series design
- Can be used to investigate the effect of a predictable event
- This design can be applied to single individuals or organizations
why is the time-series design considered quasi-experimental?
The series of observations allows a researcher to see any trends that may already exist and minimize most threats to internal validity
when are external events threats to internal validity in the time-series design?
only if it occurs simultaneously with the treatment
developmental research design
used to examine changes in behaviour related to age
two basic types of developmental research designs
- Cross-sectional design
- Longitudinal design
cross-sectional developmental research design
uses different groups of individuals, each group representing a different age. The different groups are measured at one point in time and then compared
what type of research design is the cross-sectional developmental design?
a nonexperimental nonequivalent design
strengths of the cross-sectional design
- Data can be collected in a short period
- Doesn’t require long-term cooperation between the researcher and the participants
limitations of the cross-sectional design
- The researcher can’t say anything about how a particular individual develops over time
- Factors other than age may differentiate the groups (cohort and generation effects)
cohorts
individuals who were born at roughly the same time and grew up under similar circumstances
cohort/generational effects
the differences between cohorts caused by unique experiences other than age
when are cohort effects more likely?
when there are large age differences between the groups
longitudinal developmental research design
examines development by observing or measuring a group of cohorts over time
what type of research design is the longitudinal developmental design?
a nonexperimental pre-post design
what kind of treatments are administered in the longitudinal developmental research design?
No treatment is administered; the treatment is age
strengths of the longitudinal design
- The absence of cohort effects
- You can discuss how a single individual changes with age
limitations of the longitudinal design
- Time-consuming
- Expensive
- Subject to high participant attrition, which decreases internal validity
- Potential for practice effects
participant attrition
when participants drop out of a study before completion
cross-sectional longitudinal designs
research studies that compare the results obtained from separate samples (like a cross-sectional design) that were obtained at different times (like a longitudinal design)
typical usage of cross-sectional longitudinal designs
This is typically examining the development of phenomena other than individual aging
