Research Methods: Internal Validity and Confounds

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Questions and Answers

What is the primary goal of eliminating confounding variables in an experiment?

To reduce the sample size needed

To maximize the generalizability of the findings

To ensure high internal validity (correct)

To enhance the aesthetic appeal of the experiment

In Maria's experiment, which of the following aspects is the independent variable?

The height of the feeders

The location of the feeders

The color of the feeders (correct)

The amount of seed in each feeder

What was a critical flaw in Jessie's experimental design?

Varying the time each feeder was available (correct)

Using multiple colors for feeders

Measuring the feeding over a short period

Not using the same type of seed for all feeders

Which of the following represents the dependent variable in both Maria's and Jessie's experiments?

The amount of seed eaten Signup and view all the answers

Which factor was consistent between the experiments conducted by Maria and Jessie, contributing to internal validity?

The amount of mixed birdseed used Signup and view all the answers

What can be concluded about experimental design if confounding variables are present?

The internal validity is compromised Signup and view all the answers

What role does the location of the feeders play in Maria's experiment?

It is an extraneous variable to be controlled Signup and view all the answers

Why is it important to hold certain variables constant in an experiment?

To better understand the independent variable's effect Signup and view all the answers

In the context of internal validity, what does the term 'confounding variable' refer to?

A variable that changes with the independent variable Signup and view all the answers

What would be a suitable action to improve Jessie’s experiment?

Measure all feeders simultaneously Signup and view all the answers

What is the independent variable in the experiment testing the effect of temperature on milk curdling?

Temperature of the environment Signup and view all the answers

In the context of brushing a cat more often, what is the dependent variable being measured?

Amount of fur on the furniture Signup and view all the answers

Which of the following is an example of a potential confounding variable in Elizabeth's milk experiment?

Type of container used for milk Signup and view all the answers

Which threat to internal validity involves participants dropping out of a study?

Mortality Signup and view all the answers

In the lights on/off experiment, what is the dependent variable being measured?

Cost of the electric bill Signup and view all the answers

What type of manipulation is seen when comparing brushing a cat more versus less?

Independent variable manipulation Signup and view all the answers

Which of the following is NOT a potential threat to internal validity?

Hypothesis testing Signup and view all the answers

If participants in a study become more extreme in their scores over time, which internal validity threat does this represent?

Regression to the mean Signup and view all the answers

What is a likely consequence of the maturation threat to internal validity?

Participants naturally develop or change over time Signup and view all the answers

How does the selection bias affect a study's results?

By affecting random assignment to groups Signup and view all the answers

What is the independent variable in Sam's experimental design?

Color of the feeders Signup and view all the answers

What does the dependent variable represent in Sam's experiment?

The amount of seed eaten from each feeder Signup and view all the answers

Which of the following represents a constant in Sam's experimental design?

The amount of sunflower seeds used Signup and view all the answers

Why is Sam's design considered low in internal validity?

Because multiple variables could influence the results Signup and view all the answers

What could be a confounding variable in Sam's experiment?

The number of birds visiting the feeders Signup and view all the answers

If Sam wanted to improve internal validity, which factor should he control?

Count of birds Signup and view all the answers

Which statement is true about true experiments?

They often involve manipulated independent variables. Signup and view all the answers

What role do constants play in Sam's experiment?

They ensure the results are reliable and valid. Signup and view all the answers

What aspect of Sam's experiment could lead to alternative explanations for the results?

The multiple locations chosen for the feeders Signup and view all the answers

Which statement best describes internal validity?

It shows the degree of certainty regarding cause-effect relationships. Signup and view all the answers

What is the independent variable in Rashi's study on children's and adults' preference for marshmallows?

The age group of participants Signup and view all the answers

Which factor poses a threat to internal validity in Rashi’s experimental design?

Participants' prior exposure to sweets Signup and view all the answers

What does random assignment improve in experimental research?

The control over confounding variables Signup and view all the answers

Rashi finds that 85% of children opt to eat marshmallows while only 20% of adults do. What can be classified as the dependent variable?

The preference for marshmallows Signup and view all the answers

What is a key concern when interpreting Rashi's results regarding children's and adults' taste for sweets?

Results cannot be generalized due to the sample's characteristics Signup and view all the answers

What could be a confounding variable in a study investigating the effects of diet on sleep patterns?

Participants' previous eating habits Signup and view all the answers

Which of the following is NOT a limitation of experimental research?

It requires sophisticated statistical methods Signup and view all the answers

In the context of Rashi's study, which element is critical to ensure high internal validity?

Strict control over environmental variables Signup and view all the answers

Why is it important to identify confounding variables in experimental design?

They can distort the perceived relationship between independent and dependent variables Signup and view all the answers

What is one potential drawback of conducting experiments in a laboratory setting?

Findings may not reflect real-world behaviors Signup and view all the answers

Study Notes

Internal Validity

Internal validity is a core concept in research, focusing on the degree to which a study successfully establishes a cause-and-effect relationship between variables.
It demands a clear, unambiguous demonstration that variations in the independent variable are directly responsible for observed changes in the dependent variable.
To achieve high internal validity, researchers must meticulously eliminate any alternative explanations for the results, often referred to as confounds.

Confounding Variables

Confounding variables are extraneous factors that co-vary with the independent variable, making it difficult to isolate the true effect of the independent variable.
They can cloud the interpretation of the results, leaving doubt about whether observed changes in the dependent variable are due to the independent variable or the confound.

Maria's Experimental Design

Maria's study aims to determine if birds exhibit a preference for feeders of different colors.
Her experiment comprises three identical feeders painted red, blue, and green, filled with the same birdseed and placed in a school courtyard, hanging at the same height.
While Maria controls for various factors such as feeder type, seed type, and time outside, her design might suffer from confounds related to feeder placement and bird behavior near the courtyard.

Jessie's Experimental Design

Jessie replicates Maria's goal, but uses a different placement approach.
Jessie's design introduces an additional confounding variable: Time. The feeders are not placed simultaneously due to weather conditions.
This allows environmental factors like weather to become a possible explanation for any differences in seed consumption, compromising internal validity.

Threats to Internal Validity

Maturation: Changes within participants over time, such as age, learning, or fatigue, can influence the dependent variable.
Regression to the Mean: Extreme scores tend to revert towards the average over time, potentially obscuring the true effect of the independent variable.
Selection: Differences between groups at the start of the experiment can be confounding factors, especially when participants are not randomly assigned.
Mortality: Drop-outs from the study can create biases, particularly if there's a systematic reason for participants leaving one group more than another.
Instrumentation: Changes in how the dependent variable is measured can affect the results, potentially misleading interpretations.
History: External events that occur during the experiment may influence the dependent variable and confound the results.
Testing: Repeated testing may influence subsequent responses, particularly when participants become familiar with the test or learn strategies to do better.
Selection by Maturation: When differences between pre-existing groups interact with time-related changes, it can lead to misleading interpretations.

Examples of Research Questions

Mountain Dew and Sleep: The IV is consuming Mountain Dew before bed vs. not consuming it. The DV is the amount of sleep.
Lights On and Electric Bill: The IV is leaving lights on all day vs. turning them off. The DV is the cost of the electric bill.
Cat Brushing and Fur: The IV is brushing the cat frequently vs. brushing less often. The DV is the amount of fur on furniture.
Milk Spoilage and Temperature: The IV is the temperature of storage (room temperature, fridge, low heat oven). The DV is the time it takes for the milk to curdle.

Recognizing Confounding Variables

In the milk experiment, possible confounds could be the type of milk, the size of the container, or the exposure to light.

Random Assignment

Random assignment effectively controls for pre-existing differences between participants, minimizing the impact of confounding variables.
It ensures that any potential differences between groups are likely to be due to chance rather than systematic factors.

Limitations of Experimental Research

Ethical considerations can restrict experimental designs when it is not possible to manipulate certain variables or expose participants to certain conditions.
Practical and logistical challenges may arise during conducting experiments, hindering the ability to control all variables and maintain strict experimental conditions.
The artificiality of laboratory settings can raise concerns about the generalizability of findings to real-world situations, potentially limiting the external validity of the results.

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Description

This quiz explores the concepts of internal validity and confounding variables in experimental research design. It examines how researchers can establish cause-and-effect relationships and the importance of controlling for extraneous factors. Test your understanding of these critical topics for solid research outcomes.