Midterm Lec 6a Flashcards
Quantitative research
Data are numbers and the people are subjects
Randomized control trials, chart studies
Qualitative research
Field research, case studies, participant observation and the people they study are called participants
3 key characteristics of experimental research design
1) independent variable that is manipulated
2) control of all other variables (dependent)
3) observation of the effect of the independent variable on the dependent variable
Advantages of experimental design
CRAE
Convergence,
replication,
adjustment of variables,
establishment of cause and effect relationship
3 criteria for establishing cause and effect
1) the cause must precede the effect in time
2) the cause and effect must be correlated with eachother
3) the correlation between cause and effect cannot be explained by another variable
Disadvantages of experimental design
cost
inability to generalize
securing cooperation
depending on the type you choose, it can be quite complicated to design and implement
Control or situational variables
Variables that the researcher may not be able to manipulate, exclude, remove, alter
—>Preferred way to overcome this is to hold the variable constant by the researcher
An auto manufacturer wants to know now bright brake lights should be in order to minimize the time required for the driver of a following car to realize that the car infront is stopping
Independent? Dependent? Control?
Independent, intensity brightness of brake light (manipulated)
Dependent, time of onset brake light until depression of brake pedal ( observed)
Control, colour of brake light, shape, force needed to depress pedal (hold constant)
A pigeon is trained to peck a key if a green light is illuminated but not if the light is red. Correct pecks get rewarded by access to grain. Independent? Dependent? Control?
Independent, colour of light red or green.
Dependent, number of pecks
Control, size of key and intensity of light.
Experimental group
The group that receives the treatment
Control group
The group that does not receive the treatment
Subjects
The name for the individuals in experimental research
Advantages of subjects/groups
Advantages; no chance that one treatment con contaminate another since the subject/group only receive one treatment
- each subject is compared to himself/ herself therefore differences observed are not because of differences between subject.
Disadvantages of subjects/groups
Disadvantages; concern that there is a possibility that the subjects or groups are different enough to influence the effectsof treatment.
- carryover effect: testing subjects in one condition has an effect on their testing in another condition.
How to overcome disadvantages in subjects and groups.
- Randomization of treatment levels
- counterbalancing the treatment levels, systematically vary the order of the conditions to distribute the effects of time eg practice effects, fatigue.
Random sample
A sample from the population that has been selected in an unbiased way.
Each person has an equal chance of being selected.
Random assignment
Subjects are assigned to conditions in an unbiased fashion.
Random groups design
Subjects are randomly assigned to conditions in the between subjects1 group design
Matching
- Treatment, experimental subjects are matched with a central subject
- common “matching” items: age, gender, weight, height, IQ, years of schooling
Matched group designs
Subjects are matched on some variables assumed to be correlated with the dependent variable and then randomly assigned to conditions.
Matching cautions
What characteristics or items do you match on?
Can you locate exact matches?
- true matching becomes almost impossible because there will be personal, genetic, envioumental, influences that the researcher simply can’t control.
Blind assignment
-The subject does not know whether they are in the treatment or control group
-the researcher knows what group the subject is in.
Double-blind assignment
Neither the researcher collecting the data or the subject know which group the subject belongs to.
Pre-experimental design types
-Lacks random assignment
- uses short-cuts that are much weaker than a classic experimental design
-substituted for when a researcher cannot use all the parts of the classical experimental design
- has weaker internal validity
Classic/true experimental design has
- Random assignment
- control group
-experimental group - pre-test and a post-test for each group (control + experiment)
Quasi-experimental designs
- This design is stranger than pre-experimental
- variations on classical experimental design
- used when the researcher has limited control over the independent variables
- some have… Randomization but lack pre-test, more than 2 groups
Randomized contra trial
- An experimental design for medical and pharmacutical investigation
- RCT is viewed as the best type of evidence on which to base decisions and establish guidelines
- 2 types of trials within RCT
Parallel group trial (rct)
- Only one set of patients receives the new drug
- comparison is between the two groups
Cross over trial (rct)
- All participants receive new drug
- patients are randomized into an intervention group or a control group, with the intervention group taking the medication for a selected period of time.
- after that period of time, the OG intervention group becomes the control group taking the placebo while the OG control group serves as the intervention group receiving new drug.
Populations
- The total number of people things, or events of interest
Samples
- A subset of the population
-small collection of units from a much larger collection or population - smaller set of cases selected from a larger pool
Representative sample
-the tendency to display variations among its members that are proportional to the variations that exist in the actual population of interest
-the tendency does not exist, the sample is said to be biased
Variability
- Now little, or now much the sample varies when compared to the population from which it was selected
-if there’s lots of variability, you will want a large sample in order to ensure that the sample is reasonable representative of the population - little variability then small sample size will be sufficient.
Sampling techniques
Probability and non-probability
Non-probability sampling
Aka non-random sampling
-used by qualitative researches
-seven types
Probability sampling
- Used by qualitative researches
- sampling is based on theories of probability from mathematics
-often used in experimental studies
-random is the key to sampling
Random (sampling)
- Lacks predictability, without any systematic pattern
-random samples are must likely to yield a sample that truly represents the population - lets researcher statistically calculate the relationship between the same population
Sampling error
- Now much a sample deviates from being representative of the population
Sampling element
- Unit of analysis or case in a population
- “what” are you going to study? People? Animals? Objects? Organization?