Design – the design of a study is the specification of how the research question will be answered. A research design should specify how the selection of participants, method of assignment, and choice of measures and time frame work together to accomplish the study objectives.
Interval validity – the approximate truth of inferences regarding cause-effect or casual relationships
Casual – pertaining to a cause-effect relationship
Casual relationship – a cause effect relationship. For ex. When you evaluate whether your treatment or program causes an outcome to occur, you are examining a casual relationship.
Threats to validity (3):
Single group threats – a threat to internal validity that occurs in a study that uses only a single program or treatment group and no comparison or control
Multiple-group threat – an internal validity threat that occurs in studies that use multiple groups – for instance, a program or a comparison group
Social threats to internal validity – threats to internal validity that arise because social research is conducted in real-world human contexts where people will react to not only what affects them, but also to what is happening to others around them
Three criteria must be met before you can say you have evidence for a casual (cause effect relationship): temporal precedence, covariation of the cause and effect, no plausible alternative explanations
Temporal precedence – establishing that the hypothesized cause occurs earlier in time than the effect (cause happened before your effect)
Covariation of the cause and effect - a criterion for establishing a causal relationship that hold that the cause and effect must be related or co-vary (if X then Y, if not X then not Y)
Third-variable or missing variable problem – in a two-variable cause-effect relationship, when the effect can be explained by a third variable other than cause
Plausible alternative explanation – any other cause that can bring about an effect that is different from your hypothesized or manipulated cause.
Control Group – a group, comparable to the program group that did not receive the program
Compensatory program – a program given to only those who need it on the basis of some screening mechanism (students who have low math grades receive tutoring)
History threat – a threat to internal validity that occurs when some historical event affects your study outcome. Hypothesis A specific statement of prediction (wasn’t the math program that helped students, they watched Sesame Street – chain of events)
Maturation threat – a threat to validity that is a result of natural maturation that occurs between pre- and post measurement (all events that naturally occur in one’s life that could change the outcome)
Testing threat – a threat to internal validity that occurs when taking the pretest affects how participants do on the posttest
Instrumentation threat – a threat to internal validity that arises wen the instruments (or observers) used on the posttest and the pretest differ (observers may lose interest over time)
Morality threat – a threat to validity that occurs because a significant number of participants drop out
Regression threat – a statistical phenomenon that causes a group’s average performance on one measure to regress toward or appear closer to the mean of that measure than anticipated or predicted. Regression occurs whenever you have a nonrandom sample from a population an two measures are imperfectly correlated. A regression threat will bias your estimate of the group’s posttest performance and can lead to incorrect casual inferences.
Regression to the mean:
- is a statistical phenomenon
- is a group phenomenon
- happens b/w any 2 variables
- is a relative phenomenon
- up or down
Null case – the case where the null hypothesis appears to be correct. In a two group design, for example, the null case is the finding that there is no