Ch9 307

Ch9 307

Attrition
Also known as dropout
Can occur in any research study
Comparative studies
Examine the differences between intact groups on some dependent variable of interest. There is no manipulation of the independent variable.
Correlational studies
Researcher examines the strength of relationships between variables by determining how changes in one variable are associated with changes in another variable
Correlation
Indicates the extent to which one variable is related to another variable
Exploratory studies
Conducted when little is known about the phenomenon of interest
Descriptive Studies
Phenomena are described or the relationship between variables is examined. When enough information exists to examine relationships between variables, descriptive studies may be conducted in which hypotheses are tested
Explanatory Studies
Search for causal explanations and are much more rigorous than exploratory or descriptive studies. This type of research is usually experimental.
Extraneous variables
Those variables that the researcher is not able to control, or does not choose to control, and which can influence the results of a study.
Other names are confounding, intervening variables. Also called study limitations
Internal validity
Concerns the degree to which changes in the dependent variable (effect) can be attributed to the independent variable (cause). Threats to internal validity are factors other than the independent variable that influence the dependent variable. These factors constitute rival explanations or competing hypotheses that might explain the study results.
External validity
concerns the degree to which study results can be generalized to other people and other settings.
Ex: With what degree of confidence can the study findings be transferred from the sample to the entire population? Will these study findings hold true with other groups in other times and places?
How are internal and external validity related?
As the researcher attempts to control for internal validity, external validity is usually decreased. The researcher must decide how to balance internal and external validity.
Selection bias
This threat occurs when study results are attributed to the experimental treatment or the researcher’s manipulation of the independent variable when, in fact, the results are related to subject differences before the independent variable was manipulated.
Ex: In an experiment where there will be a seminar to stop smoking, 15 volunteers who say they want to stop smoking are designated as the experimental group and 15 others who don’t indicate they wish to stop smoking are the control group. The 15 who wished to stop smoking before the experiment may have been more motivated to stop smoking before the treatment than the other 15 subjects, which may have biased the eventual results of the study.
Threat of history
Occurs when some event besides the experimental treatment occurs during the course of a study, and this event influences the dependent variable.

Ex: If a researcher is determining the incidence of breast self-examination among women after a 3 wk teaching program & during this time, an article is published in the newspaper concerning the rise in # of women w/ breast cancer, this event could result in an increase in incidence of BSE.

Maturation
Becomes a threat when changes that occur within the subjects during an experimental study influence the study results. People may become taller, older, sleepier, from the time of the pretest to the time of the posttest.
Testing threat
May occur in studies where a pretest is given or where subjects have knowledge of baseline data; may affect posttest scores.
Instrumentation change
When mechanical instruments or judges are used in the pretest and posttest phases of a study, the threat of instrumentation must be considered. Instrumentation change involves the difference between the pretest and posttest measurement caused by a change in the accuracy of the instrument or the judges’ ratings, rather than as a result of the experimental treatment.
Mortality threat
Occurs when the subjects do not complete a study
Hawthorne effect
Occurs when study participants respond in a certain manner because they are aware that they are being observed.
Experimenter effect
A threat to study results that occurs when researcher characteristics or behaviors influence subject behaviors.
Ex: facial expressions, clothing, age, gender, body build
Rosenthal effect
Indicates the influence of an interviewer on respondents’ answers. Has been shown that the researcher characteristics such as gender, dress, type of jewelry, may influence study participants’ answers to questions in nonexperimental studies
Reactive effects of the pretest
Occurs when subjects have been sensitized to the treatment because they took the pretest. May affect posttest results.
Random Assignment
Procedure that ensures that each subject has an equal chance of being assigned or placed in any of the groups in an experimental study.
True experimental designs
Those in which the researcher has a great deal of control over the research situation. Threats to the internal validity of the study are minimized. Three criteria:
1. The researcher manipulates the experimental variable(s)
2. At least one experimental and one comparison group are included in the study
3. Subjects are randomly assigned to either the experimental or the comparison group.
Manipulation
Means that the independent, or experimental, variable is controlled by the researcher. The researcher has control over the type of experimental treatment administered and who will receive the treatment.
Comparison group
A group in an experimental study that receives no treatment or a treatment that is not thought to be as effective as the experimental treatment.
Pretest-posttest control group design
The most frequently used experimental design.
A) the subjects are randomly assigned to groups
B) A pretest is given to both groups
C) the experimental group receives the experimental treatment and the comparison group receives the routine treatment or no treatment
D) a posttest is given to both groups
Posttest-only control group design
A) subjects are randomly assigned to groups
B) the experimental group receives the experimental treatment, and the comparison group receives the routine treatment or no treatment
C) a posttest is given to both groups
Solomon Four-group design
A) subjects are randomly assigned to one of the four groups
B) two of the groups, experimental group 1 and comparison group 1, are pretested
C) Two of the groups, experimental group 1 and experimental group 2, receive the experimental treatment, whereas two of the groups, comparison group 1 and comparison group 2, receive the routine treatment or no treatment
D) a posttest is given to all four groups
Quasi-experimental designs
Those in which there is either no comparison group or subjects are not randomly assigned to groups. The researcher uses existing, or intact, groups for the experimental and comparison groups.
The real world is more closely approximated than when subjects are randomly assigned to groups
nonequivalent control group design
Similar to the pretest-posttest control group design except there is no random assignment of subjects to the experimental and comparison groups
Threats to internal validity controlled by this design are history, testing, maturation, and instrumentation change.
Biggest threat to internal validity is selection bias.
Time-series design
Researcher periodically observes or measures the subjects. The experimental treatment is administered between two of the observations.
Numerous observations or measurements of the dependent variable helps strengthen the validity of the design.
Greatest threats to validity are history and testing.
Pre-experimental designs
Experimental designs that are considered very weak; researcher has little control over the research. Sometimes discussed to provide examples of how not to do research.
One-shot case study
A single group is exposed to an experimental treatment and observed after the treatment.
Threats to internal validity are history, maturation, and selection bias.

Weakest of all experimental designs because it controls for no threats to internal validity.

One-group pretest-posttest design
Provides a comparison between a group of subjects before and after the experimental treatment
Threats to internal validity are history, maturation, testing, and instrumentation change.
Correlation coefficient
The magnitude and direction of the relationship between two variables
Positive correlational relationship
also known as direct relationship
As the value of one variable increases, the value of the other variable increases.
Negative correlational relationship
also known as inverse relationship
As the value of one variable increases, the value of the other variable decreases
Retrospective studies
The dependent variable (Effect) is identified in the present (ex:a disease condition), and an attempt is made to determine the independent variable (cause of the disease) that occurred in the past.
Prospective studies
The independent variable or presumed cause (ex: high cholesterol blood levels) is identified at the present time, and then subjects are followed in the future to observe the dependent variable (ex: incidence of coronary artery disease)
Ex post facto studies
Retrospective studies often called ex post facto studies

Data is collected “after the fact”; variations in the independent variable are studied after the variations have occurred, rather than at the time of the occurrence.

Methodological Studies
concerned with the development, testing, & evaluation of research instruments and methods.
Secondary analysis studies
data are analyzed that were gathered in a previous study. Researchers may test new hypotheses or ask new research questions
Efficient and economical because data collection is usually the most expensive and time-consuming part of a study
Which of the following items distinguishes true experimental research from quasi-experimental research?
A) Size of sample
B) Use of nonprobability sample
C) Random assignment of subjects to groups
D) Introduction of an experimental treatment
C) Random assignment of subjects to groups
Which of the following designs would be most appropriate to use in trying to determine if clients’ low back pain changes after they were taught an exercise to help correct back alignment?
A) One-group pretest-posttest design
B) Posttest-only control group design
C) One-shot case study
D) Pretest-posttest control group design
D)Pretest-posttest control group design
Which of the following designs controls for the sensitization of subjects to a pretest?
A) Pretest-posttest control group design
B) Solomon four-group design
C) One-shot case study
D) Time-series design
B) Solomon four-group design
A researcher is studying the use of a new realistic model of the heart to teach people what happens during a heart attack. Two weeks later she will test their recall of the information taught. Which of the following situations that might occur during the study would concern the researcher most about the validity of her study?
A) A television celebrity had a heart attack and later announced on television that it is important for people to understand how their heart functions
B) Two of the study participants drop out of the study
C) The researcher has just learned that the new realistic heart model has increased in price.
D) The CDC released a report that the number of heart attacks has increased slightly in the last 5 years
A) A television celebrity had a heart attack and later announced on television that it is important for people to understand how their heart functions
A researcher wants to use a true experimental design in her study. However, which of the following circumstances would require the use of a quasi-experimental design rather than a true experimental design?
A) The researcher is going to administer a pretest to study participants
B) It will not be possible for the researcher to use random sampling to obtain study participants
C) The health care agency will not allow the researcher to assign study participants to groups randomly
D) The study will use a longitudinal design
C) The health care agency will not allow the researcher to assign study participants to groups randomly
Reliability
Consistency & accuracy of information obtained in a study
Statistical reliability
The same results would be obtained with a new sample of subjects
Validity
Evaluates methods to measure variables, whether the selected method measures our independent or dependent variable
Threats to internal validity
Factors that affect the dependent variables other than independent variables
Hierarchy of design for therapy question
RCT/Experimental>Quasi experimental> Cohort> Descriptive > Correlational
Hierarchy of design for prognosis question
Cohort> Case control> Descriptive correlational
Hierarchy of design for etiology/harm (prevention) question
RCT/Experimental>Quasi experimental>Cohort>Case control> Descriptive correlational