4. Measurement in the life sciences, medicine, and health

Biological systems pose particularly challenging measurement issues. This is partly because the biological domain is characterized by complexity and diversity. As a consequence, the results of measuring biological organisms will often result in a distribution of values. A further complication in medicine is that much measurement is of attributes or characteristics relating to internal or subjective phenomena such as of pain, anxiety, and dizziness. ‘Measurement in the life sciences, medicine, and health’ considers the scope of medical measurement, how to measure patients, and how to measure the health of populations. In modern medicine, there are many different reasons for taking a measurement, and hence many different types of measurement.

7. Measurement and understanding

While the quest for increased accuracy may be driven by the needs of applications, the effort to achieve accuracy of measurement itself stimulates other developments, in terms of measuring instruments and systems, and in terms of the understanding of the very nature of measurement. ‘Measurement and understanding’ explains that there are two fundamental aspects to measurement accuracy: precision (how much repeated measurements fluctuate about a central value) and bias (any systematic departure from the underlying true value, affecting all repeated measurements). It also discusses measurement and statistics and how representational measurement leads to some very deep and powerful tools for constructing models and theories about how the world works.

3. Measurement in the physical sciences and engineering

As new physical phenomena are discovered, new kinds of instruments have to be devised to measure them and old physical units are regularly redefined. It has also been necessary for measurement accuracy to increase as science and engineering has progressed. ‘Measurement in the physical sciences and engineering’ looks at the measurement of some important physical properties: length and distance; area and volume; mass, weight, and force; time; temperature; electrical and magnetic units such as electrical charge, current, potential, resistance, inductance, magnetic flux, and frequency; and measurement in quantum theory. In general, physical properties can be expressed as monomial combinations of six base attributes: charge, temperature, mass, length, time, and angle.

6. Measurement in the social sciences, economics, business, and public policy

Social measurement spans a vast range of topics. It underpins government, public policy, international relations, industrial relations, economics, academic social science research, aspects of business and commerce, and education, health, and transport systems. It is necessary for understanding our societies and how we live in them, for monitoring and indeed guiding change, to decide if things are working, and to provide accountability. ‘Measurement in the social sciences, economics, business, and public policy’ shows that, generally, social measures are aggregate measures summarizing many individual values. Statistical summaries might be based on data from every member of a population or a mere sample. It also discusses economic indicators and gaming.

2. What is measurement?

Measurement procedures can be placed on a continuum stretching from representational at one end to pragmatic at the other. Measurements in the physical sciences tend to have a heavier representational aspect, and those in the social and behavioural sciences more pragmatic. In many cases, measurement consists of a mixture of the two extremes. ‘What is measurement?’ introduces these two concepts of measurement and the properties of each perspective. Representational measurement defines a mapping from the real world to the numerical world, so that relationships between numbers represent relationships between the things being measured. Pragmatic measurement simultaneously defines an attribute and describes how to measure it.

1. A brief history

‘A brief history’ shows that measurement is at least as old as civilization. Different systems and different units of measurement were developed in different places, with the physical size of natural biological objects frequently being used as a basic unit. The key drivers for a uniform measurement system were trade, the industrial revolution, and scientific advance. In 1960 the Système International d’Units (SI units) was introduced, consisting of seven basic units: length (metre), mass (kilogram), time (second), electric current (ampere), temperature (degree kelvin), quantity of substance (mole), and luminous intensity (candela). Another twenty-two named units were defined as powers and combinations of these basic seven.

5. Measurement in the behavioural sciences

Concepts of measurement in psychology are particularly noteworthy for having encountered scepticism. While people have been happy to accept that psychological attributes can be compared, many are suspicious about the possibility of assigning numerical scores to such concepts. The earliest success stories in psychological measurement occurred in the realm of psychophysics, the area most closely linked to the physical sciences. ‘Measurement in the behavioural sciences’ explains that there are different high level purposes for which psychological measurement might be undertaken, and that these purposes require different kinds of procedures. It looks at some particular challenges of measuring the mind, including the measurement of sensation and of intelligence.