Risk assessment determines possible mishaps, their likelihood and consequences, and the tolerances for such events. The results of this process may be expressed in a quantitative or qualitative fashion. Risk assessment is an inherent part of a broader risk management strategy to help reduce any potential risk-related consequences. More precisely, risk assessment identifies and analyses potential (future) events that may negatively impact individuals, assets, and/or the environment (i.e. hazard analysis). It also makes judgments "on the tolerability of the risk on the basis of a risk analysis" while considering influencing factors (i.e. risk evaluation). Risk assessments can be done in individual cases, including in patient and physician interactions. In the narrow sense chemical risk assessment is the assessment of a health risk in response to environmental exposures. The ways statistics are expressed and communicated to an individual, both through words and numbers impact his or her interpretation of benefit and harm. For example, a fatality rate may be interpreted as less benign than the corresponding survival rate. A systematic review of patients and doctors from 2017 found that overstatement of benefits and understatement of risks occurred more often than the alternative. A 2017 systematic review from the Cochrane collaboration suggested "well-documented decision aids" are helpful in reducing effects of such tendencies or biases. An individual ́s own risk perception may be affected by psychological, ideological, religious or otherwise subjective factors, which impact rationality of the process. Individuals tend to be less rational when risks and exposures concern themselves as opposed to others. There is also a tendency to underestimate risks that are voluntary or where the individual sees themselves as being in control, such as smoking. Risk assessment can also be made on a much larger systems theory scale, for example assessing the risks of an ecosystem or an interactively complex mechanical, electronic, nuclear, and biological system or a hurricane (a complex meteorological and geographical system).