21. What is true about outliers?

Answer: C,D

Explanation:

Outliers that are miskeyed can be corrected prior to analysis and detected outliers are useful in determining if something does not belong in the study.

Outliers that are miskeyed can often be corrected before analysis, ensuring that the dataset accurately reflects the intended measurements. Additionally, detecting outliers serves a crucial function in analysis, as it helps identify data points that may not conform to expected patterns or distributions.

A) All observed outliers should be eliminated from a study prior to analysis.

This statement is incorrect as it suggests a blanket approach to outliers. While some outliers may need to be removed if they are errors or irrelevant, others may provide valuable insights, so a careful assessment of each outlier's context is necessary.

B) All outliers are statistically significant when using a normal distribution.

This option is misleading; not all outliers are statistically significant. In a normal distribution, outliers may simply reflect variability in the data, and statistical significance would need to be evaluated in terms of their influence on the overall analysis rather than assuming significance by their status as outliers.

C) Outliers that are miskeyed can be corrected prior to analysis.

This statement is accurate as it highlights the importance of data integrity. Miskeyed outliers, which arise from data entry errors or miscalculations, can and should be corrected before conducting any analysis to ensure the reliability of the results.

D) Outliers detected in a study are useful in determining if something does not belong in the study.

This statement is also correct as it emphasizes the role of outliers in exploring the dataset. Identifying outliers can reveal whether certain data points are anomalies that merit further investigation, potentially indicating issues with data collection or unique phenomena worth studying.

Conclusion

Both options C and D accurately reflect the nature and importance of outliers in data analysis. While C addresses the correction of data entry errors, D highlights the analytical value of identifying outliers as potential indicators of data integrity or unique characteristics. In contrast, options A and B present misconceptions about the treatment and significance of outliers in statistical analysis.