Experimental methods in psychology tutorial

Summary

This tutorial covers different types of experiments—lab, field, and quasi experiments—as well as experimental designs such as independent groups, repeated measures, and matched pairs. It explains the strengths and weaknesses of each type, focusing on control of variables, ecological validity, and potential biases like demand characteristics. The session emphasizes understanding the difference between experiment types and designs, including how to handle extraneous variables, minimize participant effects, and implement techniques like counterbalancing to improve the validity of experimental results.

Takeaways

• 🧪 Lab experiments are conducted in controlled environments, allowing researchers to manipulate the independent variable and minimize extraneous variables.
• 👍 One strength of lab experiments is the ability to draw stronger causal conclusions due to minimized extraneous variables.
• 👎 A weakness of lab experiments is that tasks can lack realism, making them less applicable to real-world situations, and participants may show demand characteristics.
• 🌳 Field experiments take place in natural settings, where participants may not know they're part of an experiment, leading to more natural behavior.
• 😊 Field experiments have fewer demand characteristics and greater ecological validity, making the results more generalizable to real-life contexts.
• ⚠️ However, field experiments lack control over extraneous variables and are harder to replicate due to inconsistent conditions.
• 🌿 Quasi-experiments involve naturally occurring independent variables, such as age or gender, with high ecological validity but weaker control over variables and difficulty establishing causality.
• 🚗 Experimental designs include independent groups, repeated measures, and matched pairs, each with its strengths and weaknesses.
• 📋 In independent groups design, participants only engage in one experimental condition, but participant differences between groups may introduce extraneous variables.
• 🔄 Repeated measures design involves the same participants in all conditions, reducing participant variables but potentially introducing order effects like boredom or practice, mitigated by counterbalancing.

Q & A

What is the difference between a type of experiment and an experimental design?

A type of experiment refers to where and how the experiment is conducted, such as lab, field, or quasi experiments. Experimental design, on the other hand, refers to how participants are allocated to different conditions, including independent groups, repeated measures, and matched pairs designs.

What is a lab experiment, and what are its key strengths?

A lab experiment is conducted in a controlled environment where the independent variable is deliberately manipulated by the researcher. Its key strengths include control over extraneous variables, allowing for more causal conclusions, and ensuring that the independent variable affects the dependent variable without interference from other factors.

What are the weaknesses of lab experiments?

Lab experiments can lack mundane realism, meaning the tasks participants perform may be artificial and unrealistic. Additionally, participants may show demand characteristics by behaving in a way they believe the researcher wants them to, potentially skewing the results.

What is a field experiment, and how does it differ from a lab experiment?

A field experiment is conducted in a natural environment where participants may not know they are part of an experiment. Unlike lab experiments, field experiments have higher ecological validity, as participants behave more naturally, but there is less control over extraneous variables, making it harder to replicate and control results.

What are the strengths of field experiments?

Field experiments have fewer demand characteristics because participants are often unaware they are part of an experiment, leading to more natural behavior. They also have greater ecological validity, meaning the results can be better generalized to real-life situations.

What is a quasi-experiment and what is its key characteristic?

A quasi-experiment, or natural experiment, is one where the independent variable is naturally occurring, such as differences in age, race, or gender. The researcher cannot manipulate these variables, making it different from lab or field experiments.

What are the weaknesses of quasi-experiments?

Since the independent variable cannot be controlled by the researcher, it is harder to establish cause-and-effect relationships. Additionally, quasi-experiments are difficult to replicate because the naturally occurring variables cannot be manipulated.

What is an independent groups design in experimental research?

In an independent groups design, participants are divided into different groups, each of which only takes part in one experimental condition. For example, one group might participate in condition A, while another group participates in condition B.

What is a repeated measures design, and what are its potential issues?

In a repeated measures design, all participants take part in all experimental conditions. A potential issue is that participants might experience practice effects, becoming more skilled at a task as they go through the conditions, or become bored and tired, which could affect the results.

What is a matched pairs design, and how does it minimize extraneous variables?

A matched pairs design attempts to reduce participant variables by pairing participants with similar key characteristics, such as age, IQ, or handedness. Each member of the pair is then placed in a different experimental condition, which helps compare 'like-for-like' and minimize extraneous variables.