What Is a Scale?

A scale is a graduated line used for measuring. Thousands of scales have been developed to measure a variety of social, psychological and health behaviors and experiences.

The purpose of this article is to review current practices and main limitations reported in the literature regarding scale development. Ultimately, this should allow for a more informed and precise design of future scales.


A scale is a ratio used to represent real-world objects in proportional sizes. It helps us shrink huge lands into maps or blueprints and work with smaller models of machinery, buildings, and structures. It allows engineers and architects to visualize their plans before they start building on the ground.

Musical scales are systems of pitches in a particular range. Each scale has a distinct pattern of interval relationships between its tones. This basic property defines a scale, while other aspects of pitch usage, such as the choice of tones or the way they are used, may be significant to the overall sound of a piece of music.

The term “scale” can also be used to describe the size or extent of something, such as an event or problem. For example, you might say that someone stole food aid on a large scale or that an earthquake was measured on a large scale. You might even use the word to describe how much you get paid for a job or how fast your car can go on a particular road.


The word scale can be used to describe a variety of things. For example, a person can scale a mountain to climb it. A musical scale is a set of tones that can be used to create melodies and harmony. There are many different scales, including the major scale, minor scale and diatonic scale. Musicologists have classified these different types of scales into various categories, such as chromatic scales and Lydian scales.

The concept of scale can also be used to refer to a nation or country. A national analysis scale is a type of evaluation that is carried out by government agencies and other organizations at the national level. A national analysis scale can help to identify problems and issues that affect the entire nation.

There are also scales that can be applied to a specific person, such as the Likert scale question. This question type is often seen on surveys and questionnaires, and it can help to rate a person’s feelings or beliefs.


The reliability of a scale refers to the consistency of the measure. A measure that is not reliable will be inaccurate. A reliable scale will produce consistent and similar results across different respondents. It is also important to make sure that a measure is not subject to random error (also called variance). For example, if a questionnaire asks how many grievances an individual has in a month as a way of measuring morale, there could be differences between responses because the respondents might interpret “grievance” differently, and the measurement would therefore be unreliable.

The most commonly used measure of internal consistency is Cronbach’s alpha. This can be calculated from a set of Likert items by selecting Analyze -> Scale -> Reliability Analysis. This will produce a table with the following columns:


Scale validity is the extent to which a measurement tool measures what it purports to measure. It is generally determined through an empirical process which relies on a variety of different types of evidence including face, construct and predictive validity (1, 2).

For instance, content validity requires that the items included in a scale adequately measure the phenomenon underlying the construct being measured (25). This is assessed using various techniques such as cognitive interviews which assess face validity (26) or through cross-sectional or longitudinal test-retest data (27) to evaluate the extent to which items retain their construct relevance across repeated administrations.

Construct validity is the extent to which a scale has a good relationship with a well-defined theoretical construct (21). This is assessed by using correlations and latent variable models. Predictive validity is the ability of a measurement to predict performance on a criterion, such as a selection test score or the willingness of a mother to exclusively breastfeed (28). Concurrent criterion validity refers to the degree to which a measurement correlates with another measure taken at the same time, typically used as a gold standard, to estimate convergent validity.

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