Inferential Statistics
- Inferential Statistics – Definition, Types, Examples, Formulas
- Observational Studies and Experiments
- Sample and Population
- Sampling Bias
- Sampling Methods
- Research Study Design
- Population Distribution, Sample Distribution and Sampling Distribution
- Central Limit Theorem
- Point Estimates
- Confidence Intervals
- Introduction to Bootstrapping
- Bootstrap Confidence Interval
- Paired Samples
- Impact of Sample Size on Confidence Intervals
- Introduction to Hypothesis Testing
- Writing Hypotheses
- Hypotheses Test Examples
- Randomization Procedures
- p-values
- Type I and Type II Errors
- P-value Significance Level
- Issues with Multiple Testing
- Confidence Intervals and Hypothesis Testing
- Inference for One Sample
- Inference for Two Samples
- One-Way ANOVA
- Two-Way ANOVA
- Chi-Square Tests
Control and Placebo Groups
Control and Placebo Groups
Control and placebo groups are two types of groups that are commonly used in research studies, particularly in clinical trials.
The control group is a group of participants who are not exposed to the intervention being studied. The purpose of the control group is to provide a comparison against which the effects of the intervention can be evaluated. For example, in a study evaluating the effectiveness of a new drug, the control group would receive a placebo or standard treatment, while the intervention group would receive the new drug.
The placebo group is a type of control group that receives a treatment that appears identical to the intervention being studied but contains no active ingredients. The purpose of the placebo group is to control for the placebo effect, which is a phenomenon where a participant’s belief in a treatment can lead to an improvement in their symptoms, even if the treatment is ineffective. For example, in a study evaluating the effectiveness of a new pain medication, the placebo group would receive a sugar pill that looks identical to the actual medication.
- Control Group
- A level of the explanatory variable that does not receive an active treatment; they may receive no treatment or a placebo
- Placebo Group
- A group that receives what, to them, appears to be a treatment, but actually is neutral and does not contain any active treatment (e.g., a sugar pill in a medication study)
Example: Weight Loss Supplement Study
A group of researchers are conducting a study to determine the effectiveness of a new weight loss supplement on reducing body fat in overweight individuals.
Control Group: The researchers recruit 100 overweight participants and randomly assign them to either the control group or the experimental group. The control group receives a placebo pill that looks identical to the weight loss supplement but contains no active ingredients. The participants in the control group are instructed to take the pill daily for 12 weeks, just like the experimental group. The control group is monitored for any changes in body fat percentage, weight, or other relevant measures, just like the experimental group.
Experimental Group: The remaining 100 overweight participants are assigned to the experimental group and receive the actual weight loss supplement being tested. They are also instructed to take the supplement daily for 12 weeks. The experimental group is monitored for changes in body fat percentage, weight, and other relevant measures throughout the study.
By comparing the outcomes of the control group to the experimental group, the researchers can determine if any observed effects are due to the weight loss supplement or simply the result of chance or natural variation. By using a placebo control group, the researchers can also determine if any observed effects are due to the placebo effect or other non-specific factors, such as changes in diet or exercise habits. This helps to ensure that the observed effects are actually due to the weight loss supplement being tested, and not simply due to chance or the placebo effect.