Experimental Design, Group Allocation, and Sources of Research Bias
Requirements and Design of Experimental Research
Guidelines for Experimental Execution:
Standardized guidelines ensure that specific methodological requirements are rigorously met during an experiment.
Experimental research imposes additional, strict requirements compared to correlational research, moving beyond mere association to establish causal conclusions.
Hypothesis Formulation and Spurious Relationships:
Hypotheses are formulated either through direct observations or systematic reviews of past research and established theory to make informed predictions.
Informed predictions are necessary to prevent the identification of spurious relationships—correlations that appear between variables when there is no logical or theoretical basis for why they should exist.
Core Variables and Experimental Manipulation:
Experimental design requires manipulating a variable in some way so that participants do not all share the exact same experience.
Independent Variables (IVs): Represent the predictors manipulated by the researcher.
Dependent Variables (DVs): Represent the outcome variables of interest being measured.
Experimental and Control Groups
The Experimental Group:
Consists of the group of participants where the experimental manipulation is actively taking place.
Represents the primary phenomenon or variable under investigation.
The Control Group:
Consists of participants who do not experience the manipulated experimentation.
Serves as an essential baseline for comparison; without a comparison group, no valid conclusions can be drawn regarding whether a manipulation had any effect.
Controls for chance factors and random noise that might otherwise influence or distort the study's results.
Sample Allocation and Internal Validity:
In a study with a sample population (e.g., participants), subjects are divided into two primary groups: an experimental group and a control group.
Dividing participants across experimental and control conditions accounts for participant-level and external variations, including:
Differences in age
Differences in gender
Differences in environmental factors
Rule out external threats to internal validity to ensure that outcome changes are attributable solely to the variable manipulation.
Sources of Bias in Research Design
Primary Sources of Bias:
When designing an experimental study, special attention must be paid to bias, which originates from two general sources: experimenter bias and participant bias.
Experimenter Bias:
Occurs when a researcher's expectations skew the results of the study.
Directly linked to confirmation bias, wherein individuals naturally tend to seek out information that affirms their existing beliefs, predictions, or hypotheses.
Manifests when a researcher exerts influence through small interactions or subtle adjustments in the wording of questions, inadvertently skewing participant responses to align with their pre-existing beliefs.
Refers specifically to biases originating from the person conducting the experiment.
Participant Bias:
Refers to biases introduced by the individuals participating in the study as they observe or react to the research setting.
Questions and Discussion
Group Distinctions in Research:
Inquiry into whether there are any questions regarding the operational differences between the experimental group and the control group in an experimental study.