# Statistics for Public Health

## STATISTICS FOR PUBLIC HEALTH

Nearly every day statistics are used to support assertions about health and what people can do to improve their health. The press frequently quotes scientific articles assessing the roles of diet, exercise, the environment, and access to medical care in maintaining and improving health. Because the effects are often small, and vary greatly from person to person, an understanding of statistics and how it allows researchers to draw conclusions from data is essential for every person interested in public health. Statistics is also of paramount importance in determining which claims regarding factors affecting our health are not valid, not supported by the data, or are based on faulty experimental design and observation.

When an assertion is made such as "electromagnetic fields are dangerous," or "smoking causes lung cancer," statistics plays a central role in determining the validity of such statements. Methods developed by statisticians are used to plan population surveys and to optimally design experiments aimed at collecting data that allows valid conclusions to be drawn, and thus either confirm or refute the assertions. Biostatisticians also develop the analytical tools necessary to derive the most appropriate conclusions based on the collected data.

## ROLE OF BIOSTATISTICS IN PUBLIC HEALTH

In the Institute of Medicine's report The Future of Public Health, the mission of public health is defined as assuring conditions in which people can be healthy. To achieve this mission three functions must be undertaken: (1) assessment, to identify problems related to the health of populations and determine their extent; (2) policy development, to prioritize the identified problems, determine possible interventions and/or preventive measures, set regulations in an effort to achieve change, and predict the effect of those changes on the population; and (3) assurance, to make certain that necessary services are provided to reach the desired goal—as determined by policy measures—and to monitor how well the regulators and other sectors of the society are complying with policy.

An additional theme that cuts across all of the above functions is evaluation, that is, how well are the functions described above being performed.

Biostatistics plays a key role in each of these functions. In assessment, the value of biostatistics lies in deciding what information to gather to identify health problems, in finding patterns in collected data, and in summarizing and presenting these in an effort to best describe the target population. In so doing, it may be necessary to design general surveys of the population and its needs, to plan experiments to supplement these surveys, and to assist scientists in estimating the extent of health problems and associated risk factors. Biostatisticians are adept at developing the necessary mathematical tools to measure the problems, to ascertain associations of risk factors with disease, and creating models to predict the effects of policy changes. They create the mathematical tools necessary to prioritize problems and to estimate costs, including undesirable side effects of preventive and curative measures.

In assurance and policy development, biostatisticians use sampling and estimation methods to study the factors related to compliance and outcome. Questions that can be addressed include whether an improvement is due to compliance or to something else, how best to measure compliance, and how to increase the compliance level in the target population. In analyzing survey data, biostatisticians take into account possible inaccuracies in responses and measurements, both intentional and unintentional. This effort includes how to design survey instruments in a way that checks for inaccuracies, and the development of techniques that correct for nonresponse or for missing observations. Finally, biostatisticians are directly involved in the evaluation of the effects of interventions and whether to attribute beneficial changes to policy.