You have estimated the correlation between exposure to noise (independent variable) and hearing loss (dependent variable) among factory workers. Both exposure and outcome measures were collected as continuous variables. The statistical analysis showed a Pearson r of 0.4 and the correlation between the two variables was highly significant at p < 0.001.

Part 1: Can one argue that the relationship between the investigated exposure and outcome is causal? Explain your answer.

Part 2: How likely is the possibility that the results were a mere chance finding? Explain your answer.

Part 3: You were requested to again investigate the association between exposure to noise and hearing loss while also accounting for each worker's age, level of education, history of a hearing ailment, and presence of comorbidity. What statistical analysis would provide an answer?

Part 4: After you have analyzed Part 3, the association between exposure to noise and hearing loss weakened and became statistically insignificant. Explain this finding.