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experimental design

Representative Sample: Definition, Uses & Methods

By Jim Frost Leave a Comment

What is a Representative Sample?

A representative sample is one where the individuals in the sample reflect the properties of an entire population. Use a representative sample when you want to generalize the results from the sample to a population. By studying a representative sample, you can approximate the properties of the population from which it was drawn. [Read more…] about Representative Sample: Definition, Uses & Methods

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Sampling Methods: Different Types in Research

By Jim Frost 2 Comments

What Are Sampling Methods?

Sampling methods are the processes by which you draw a sample from a population. When performing research, you’re typically interested in the results for an entire population. Unfortunately, they are almost always too large to study fully. Consequently, researchers use samples to draw conclusions about a population—the process of making statistical inferences. [Read more…] about Sampling Methods: Different Types in Research

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Cohort Study: Definition, Benefits & Examples

By Jim Frost Leave a Comment

What is a Cohort Study?

A cohort study is a longitudinal experimental design that follows a group of participants who share a defining characteristic. For example, a cohort study can select subjects who have exposure to a risk factor, are in the same profession, population or generation, or experience a particular event, such as a medical procedure. This design determines whether exposure to a risk factor affects an outcome. [Read more…] about Cohort Study: Definition, Benefits & Examples

Filed Under: Basics Tagged With: conceptual, experimental design

Case Control Study: Definition, Benefits & Examples

By Jim Frost 2 Comments

What is a Case Control Study?

A case control study is a retrospective, observational study that compares two existing groups. Researchers form these groups based on the existence of a condition in the case group and the lack of that condition in the control group. They evaluate the differences in the histories between these two groups looking for factors that might cause a disease. [Read more…] about Case Control Study: Definition, Benefits & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, interpreting results

Simple Random Sampling: Definition & Examples

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What is Simple Random Sampling?

Simple random sampling (SRS) is a probability sampling method where researchers randomly choose participants from a population. All population members have an equal probability of being selected. This method tends to produce representative, unbiased samples. [Read more…] about Simple Random Sampling: Definition & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Convenience Sampling: Definition & Examples

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What is Convenience Sampling?

Convenience sampling is a non-probability sampling method where researchers use subjects who are easy to contact and obtain their participation. Researchers find participants in the most accessible places, and they impose no inclusion requirements. Convenience sampling is also known as opportunity or availability sampling. [Read more…] about Convenience Sampling: Definition & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Systematic Sampling: Definition, Advantages & Examples

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What is Systematic Sampling?

Systematic sampling is a probability sampling method for obtaining a representative sample from a population. To use this method, researchers start at a random point and then select subjects at regular intervals of every nth member of the population. Like other probability sampling methods, the researchers must identify their population of interest before sampling from it. [Read more…] about Systematic Sampling: Definition, Advantages & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Validity in Research and Psychology: Types & Examples

By Jim Frost 2 Comments

What is Validity in Psychology, Research, and Statistics?

Validity in research, statistics, psychology, and testing evaluates how well test scores reflect what they’re supposed to measure. Does the instrument measure what it claims to measure? Do the measurements reflect the underlying reality? Or do they quantify something else? [Read more…] about Validity in Research and Psychology: Types & Examples

Filed Under: Basics Tagged With: conceptual, experimental design

Internal and External Validity

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Internal and external validity relate to the findings of studies and experiments. [Read more…] about Internal and External Validity

Filed Under: Basics Tagged With: conceptual, experimental design

Cluster Sampling: Definition, Advantages & Examples

By Jim Frost 1 Comment

What is Stratified Sampling?

Cluster sampling is a method of obtaining a representative sample from a population that researchers have divided into groups. An individual cluster is a subgroup that mirrors the diversity of the whole population while the set of clusters are similar to each other. Typically, researchers use this approach when studying large, geographically dispersed populations because it is a cost-controlling measure. [Read more…] about Cluster Sampling: Definition, Advantages & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Stratified Sampling: Definition, Advantages & Examples

By Jim Frost 2 Comments

What is Stratified Sampling?

Stratified sampling is a method of obtaining a representative sample from a population that researchers have divided into relatively similar subpopulations (strata). Researchers use stratified sampling to ensure specific subgroups are present in their sample. It also helps them obtain precise estimates of each group’s characteristics. Many surveys use this method to understand differences between subpopulations better. Stratified sampling is also known as stratified random sampling. [Read more…] about Stratified Sampling: Definition, Advantages & Examples

Filed Under: Basics Tagged With: conceptual, experimental design, sampling methods

Control Variables: Definition, Uses & Examples

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What is a Control Variable?

Control variables, also known as controlled variables, are properties that researchers hold constant for all observations in an experiment. While these variables are not the primary focus of the research, keeping their values consistent helps the study establish the true relationships between the independent and dependent variables. Control variables are different from control groups. [Read more…] about Control Variables: Definition, Uses & Examples

Filed Under: Basics Tagged With: conceptual, experimental design

Control Group in an Experiment

By Jim Frost 3 Comments

A control group in an experiment does not receive the treatment. Instead, it serves as a comparison group for the treatments. Researchers compare the results of a treatment group to the control group to determine the effect size, also known as the treatment effect. [Read more…] about Control Group in an Experiment

Filed Under: Basics Tagged With: conceptual, experimental design

Independent and Dependent Variables: Differences & Examples

By Jim Frost 6 Comments

Scientist at work on an experiment consider independent and dependent variables.Independent variables and dependent variables are the two fundamental types of variables in statistical modeling and experimental designs. Analysts use these methods to understand the relationships between the variables and estimate effect sizes. What effect does one variable have on another?

In this post, learn the definitions of independent and dependent variables, how to identify each type, how they differ between different types of studies, and see examples of them in use. [Read more…] about Independent and Dependent Variables: Differences & Examples

Filed Under: Regression Tagged With: conceptual, experimental design

Independent and Dependent Samples in Statistics

By Jim Frost 14 Comments

When comparing groups in your data, you can have either independent or dependent samples. The type of samples in your experimental design impacts sample size requirements, statistical power, the proper analysis, and even your study’s costs. Understanding the implications of each type of sample can help you design a better experiment. [Read more…] about Independent and Dependent Samples in Statistics

Filed Under: Basics Tagged With: analysis example, choosing analysis, conceptual, experimental design

Observational Studies Explained

By Jim Frost 6 Comments

Observational studies use samples to draw conclusions about a population when the researchers do not control the treatment, or independent variable, that relates to the primary research question.

Random assignment reduces systematic differences between experimental groups at the beginning of the study, which increases your confidence that the treatments caused any differences between groups you observe at the end of the study.

Unfortunately, using random assignment is not always possible. For these cases, you can conduct an observational study. In this post, learn about observational studies, why these studies must account for confounding variables, and how to do so. I’ll close this post by reviewing a published observational study about vitamin supplement usage. [Read more…] about Observational Studies Explained

Filed Under: Basics Tagged With: conceptual, experimental design

Random Assignment in Experiments

By Jim Frost 4 Comments

Random assignment uses chance to assign subjects to the control and treatment groups in an experiment. This process helps ensure that the groups are equivalent at the beginning of the study, which makes it safer to assume the treatments caused any differences between groups that the experimenters observe at the end of the study. [Read more…] about Random Assignment in Experiments

Filed Under: Basics Tagged With: conceptual, experimental design, interpreting results

Repeated Measures Designs: Benefits and an ANOVA Example

By Jim Frost 20 Comments

Repeated measures designs, also known as a within-subjects designs, can seem like oddball experiments. When you think of a typical experiment, you probably picture an experimental design that uses mutually exclusive, independent groups. These experiments have a control group and treatment groups that have clear divisions between them. Each subject is in only one of these groups. [Read more…] about Repeated Measures Designs: Benefits and an ANOVA Example

Filed Under: ANOVA Tagged With: analysis example, conceptual, experimental design, interpreting results

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