Also being male and young were associated with high burnout rates, whilst involvement in religious activity were associated with lower burnout rates. The child worker whose job status was that of professional was more likely to show burnout and compassion fatigue than another not of that status.

The variables here were dependent variable -- burnout and stress, independent variable -- status of the worker as well as personality and environmental characteristics (namely those described above).. Explain how the research exemplifies regression discontinuity or correlation research, and identify the specific design, if appropriate.

This is an example of correlation research. The researchers wished to see whether any specific factors were associated with burnout and stress and whether the occurrence of these variables showed positive association (or negative association) with an increase or decrease of stress / burnout. Analyze the aspects of the research that enabled the researcher to draw conclusions about the results. Include a description of the threats to validity that are particularly relevant to this study, and describe what the researcher did to reduce these threats.

The researchers used a reliable instrument to assess the...

They also noted applicable and exhaustive demographic data. The threats to validity may have been the fact that participant's stress was related to factors other than work. The researchers, therefore, chose an instrument whose function was to solely measure work-related stress.
Explain how various design elements affected the researcher's conclusions.

The survey that was used explicitly measured work-related stress. The researchers were exhaustive in their demographical observations. These included race, gender, dwelling place, socio-economic status, occupation, status, age, and particulars of living condition. If a significant part of the sample were, for instance, male and simultaneously showed a greater increase in work-related stress than females did, the researchers concluded that male child welfare workers were more apt to evidence stress than females.

Source

Sprang, G et al. Secondary Traumatic Stress and Burnout in Child Welfare Workers: A Comparative Analysis of Occupational Distress Across Professional Groups Child Welfare, 90, 149-168

Urban Institute. Impact Evaluation: Regression Discontinuity.

http://www.urban.org/toolkit/data-methods/regression.cfm