1.19:

1.19: 统计显著性

Statistical Significance

JoVE Core
Social Psychology

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JoVE Core Social Psychology

Statistical Significance

1.18: Variation: Normal Distribution, Range, and Standard Deviation

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01:50 min

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February 12, 2020

Overview

Once data is collected from both the experimental and the control groups, a statistical analysis is conducted to find out if there are meaningful differences between the two groups. A statistical analysis determines how likely any difference found is due to chance (and thus not meaningful). In psychology, group differences are considered meaningful, or significant, if the odds that these differences occurred by chance alone are 5 percent or less. Stated another way, if we repeated this experiment 100 times, we would expect to find the same results at least 95 times out of 100.

The greatest strength of experiments is the ability to assert that any significant differences in the findings are caused by the independent variable. This occurs because random selection, random assignment, and a design that limits the effects of both experimenter bias and participant expectancy should create groups that are similar in composition and treatment. Therefore, any difference between the groups is attributable to the independent variable, and now we can finally make a causal statement. If we find that watching a violent television program results in more violent behavior than watching a nonviolent program, we can safely say that watching violent television programs causes an increase in the display of violent behavior.

Transcript

After researchers collect empirical data from a predetermined sample size, they can follow up with statistical analyses to determine whether the differences they observed between groups or variables are meaningful or the result of chance alone.

For example, perhaps a researcher finds that undergraduate students who were asked to use gesture and emotional expression to act out a scene—the experimental group—remembered more of their lines than students who read them without using gesture and emotional expression—the control group.

Now she wants to know the likelihood that this difference occurred because the experimental manipulation affected participants’ memory for the lines, rather than because of random happenstance.

To accomplish this task, she needs to establish the p-value—the probability that the difference between the groups occurred by chance.

If she finds that the p-value is 0.05 or below—meaning there is a five percent or less possibility the result occurred by chance—then the difference between the groups is considered statistically significant by convention.

In other words, there is at least a 95 percent chance that participants in the experimental group remembered more lines because of the experimental manipulation—using gesture and emotional expression.

As a result, she can confidently accept the alternative or experimental hypothesis—that the experimental manipulation affected the results—and reject the null hypothesis—that the experimental manipulation had no effect.

In the end, if research findings are found to be statistically significant, the results are considered meaningful differences by the scientific community.

Key Terms and definitions

Statistical analysis - Formal process of investigating relationships among variables, applied in psychology.
Statistically significant - A measure of the likelihood that the difference is explaining by chance.
P-value - A statistical term for the probability that an observed result occurred by chance.
Significant difference - Noticeable variance between groups, not likely to be purely by chance.
Independent variable - The variable in the experiment that is manipulated, causing an effect.

Learning Objectives

Define Statistical analysis - Explain how it is used in psychology (e.g., statistical analysis).
Contrast statistically significant vs. P-value - Explain what sets these two terms apart (e.g., significant difference).
Explore p-value - Describe its role in statistical analysis (e.g., p-value).
Explain independent variable - Discuss its influence in an experiment.
Apply significant difference - Contextualize this on experimental scenarios.

Questions that this video will help you answer

What is statistical analysis and how is it applied in psychology?
What is the difference between statistically significant and p-value?
How is p-value used when conducting statistical analysis?

This video is also useful for

Students - Understand how statistical analysis supports learning in experimental psychology
Educators - Provides a clear framework for teaching statistical analysis in psychology
Researchers - Relevance of statistical significance and p-value in scientific studies
Psychology Enthusiasts - Offer insights about statistical analysis and its significance in psychology

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JoVE Core Psych JoVE Core Psych Chapter 1 JoVE Core Psych Lesson 618