Explain the relationship between statistical significance and effect size.

To prepare for this assignment:
Review Chapter 8 in your course text, Research Methods for the Behavioral Sciences. Pay attention to the importance of statistical significance and effect size.
Consider the relationship between statistical significance and effect size.
Using the Walden Library, select and review two or three forensic psychology research articles where “effect size” was reported.
Consider what role effect size played in the statistical significance of the studies you selected.
The assignment (1–3 pages):
Explain the relationship between statistical significance and effect size.
Explain the importance of effect size in the statistical significance of the studies you reviewed.
Support your Assignment with specific references to all resources used in its preparation. You are asked to provide a reference list only for those resources not included in the Learning Resources for this course.
ANSWER
Relationship Between Statistical Significance and Effect Size
Statistical significance is the probability of obtaining a result as extreme or more extreme than the one obtained, assuming that the null hypothesis is true. It is typically measured using a p-value, which is the probability of obtaining a result as extreme or more extreme than the one obtained, assuming that the null hypothesis is true.
Effect size is a measure of the magnitude or strength of a relationship between two variables. It is not influenced by the sample size, while statistical significance is. There are many different measures of effect size, such as Cohen’s d, Pearson’s r, and eta squared.
The relationship between statistical significance and effect size can be complex. A statistically significant result does not necessarily mean that there is a meaningful effect size. For example, a study with a large sample size may find a statistically significant difference between two groups, even if the effect size is very small.
On the other hand, a study with a small sample size may fail to find a statistically significant difference between two groups, even if the effect size is large. This is because statistical significance is dependent on both the effect size and the sample size.
Role of Effect Size in the Statistical Significance of Forensic Psychology Research Articles
Effect size is an important consideration in forensic psychology research because it can help to determine the practical significance of the findings. A statistically significant result with a small effect size may not be practically significant, while a statistically significant result with a large effect size may be more practically significant.
For example, a study may find that a new treatment for recidivism is statistically significantly more effective than the standard treatment. However, if the effect size is small, the new treatment may not be worth the additional cost or effort.
On the other hand, a study may find that a new risk assessment tool is statistically significantly more accurate than the standard risk assessment tool. If the effect size is large, the new tool may be worth adopting, even if it is more expensive or time-consuming to use.
Examples of Effect Size in Forensic Psychology Research Articles
Here are a few examples of how effect size was reported in forensic psychology research articles:
Study 1: A study by Borum et al. (2013) examined the effectiveness of a cognitive-behavioral therapy (CBT) program for reducing recidivism among sex offenders. The study found that the CBT program was statistically significantly more effective than the standard treatment program. The effect size was large (Cohen’s d = 0.80).
Study 2: A study by Hanson et al. (2001) developed a risk assessment tool for predicting recidivism among violent offenders. The tool was found to be statistically significantly more accurate than the standard risk assessment tool. The effect size was large (AUC = 0.75).
Study 3: A study by Grisso et al. (2003) examined the accuracy of eyewitness testimony. The study found that eyewitness testimony was statistically significantly less accurate when the witnesses were exposed to misleading information. The effect size was small (Cohen’s d = 0.20).
Conclusion
Effect size is an important consideration in forensic psychology research because it can help to determine the practical significance of the findings. A statistically significant result with a small effect size may not be practically significant, while a statistically significant result with a large effect size may be more practically significant.
When interpreting the results of forensic psychology research studies, it is important to consider both the statistical significance and the effect size.