(3) experimental research design

• in the experiment design treatments are applied to experimental units, thus we call them as treatment group
• in comparative experiments, member of the complementary group, the control group, receive no treatment or a standard treatment.
• types of experimental research design:

  1. pre-experimental design
  2. quasi-experimental design
  3. true experimental design
• pre-experimental design - follow basic experimental steps but does not include a control group
• pre-experimental design - a single group is often studies but no comparison between an equivalent non-treatment group is made.
• pre-experimental design - it is applied to experimental research design with the least internal validity
• kinds of pre-experimental design

  1. one-shot case study design
  2. one group pretest posttest study
• one-shot case study design - subjects are presented with some type of treatment and then the outcome measured is applied
• one-shot case study design - a single group is studied at a single point in time after some treatment that is presumed to have caused change.
• one-shot case study design - no control or comparison group is employed
• one-shot case study design - X0_2 (treatment * posttest)
• one group pretest posttest study - a pretest is included to determine baseline scores of the sample. A posttest is then administered to measure the effect of the treatment used.
• one group pretest posttest study - this design has also one group receiving treatment but with no non-treatment group to compare with
• one group pretest posttest study - 0_1X0_2 (pretest * treatment *posttest)
• quasi-experimental design - the prefix quasi means "resembling". Thus this research that resembles experimental research but is not true-experimental research.
• quasi-experimental design - although the independent variable is manipulated, participants are not randomly assigned to conditions or orders of conditions
• quasi-experimental design - most likely to be conducted in field settings in which random assignment is difficult or impossible
• quasi-experimental design - they are often conducted to evaluate the effectiveness of a treatment-- perhaps a type of psychotherapy or an educational intervention
• quasi-experimental design - involves the manipulation of an independent variable without the random assignment of participants to conditions or orders of conditions
• kinds of quasi-experimental design

  1. non-equivalent control group design
  2. interrupted time series design
• non-equivalent control group design - when participants are not randomly assigned to conditions, the resulting groups are likely to be dissimilar in some ways.
• interrupted time series design - employs multiple measures before and after the experimental intervention
• interrupted time series design - users of this design assume that the time threats such as history or maturation appear as regular changes in the measures prior to intervention.
• a time series is a set of measurements taken at intervals over a period of time.
• true experimental design - it controls both time-related and group-related threats.
• true experimental design - there are two or more differently treated groups and random assignment to those groups
• true experimental design - it has the highest internal validity of all the experimental research design
• true experimental design - one in which the researcher manipulates the independent variable to observe its effect on some behavior or cognitive process while using random assignment of participants to groups in order to control external factors from influencing the results.
• manipulation - control of independent variable by the researcher through treatment or intervention
• control - the use of control group and extraneous variables on the dependent variable.
• randomization - every subject gets equal chance being assigned to experimental and control group