Likert scale

The Likert scale ( Likert after Rensis ) is a method for measuring personal settings that are queried by means of so -called items. The items are positively or negatively worded statements about an issue to which the respondents approval or rejection in several predetermined gradations can express. The possible answers are designed so that the " distance" between the response options is as equal as possible (equidistance ).

Construction

The basic idea

The methodological consideration is the following: We want to know concerning the setting of the subject, a particular object. All related items are formulated as a strictly positive or negative statements. The Likert scale is based on the consideration that the subject is the statement of an item declines even more, depending on their attitude differs from the wording of the item. As a whole, then the answers to the degree of the settings are displayed. It is hoped that this approach methodologically durable measurement of attitude.

In the concrete execution of a questionnaire, the answer choices for an item form from the degree of approval or disapproval of respondent to testify of the item. The possible answers are coded as natural numbers and arranged in ascending order.

Answers on a Likert scale are formally ordinal or ranking scales, since it can not necessarily be assumed that test participants perceive the possible answers as equidistant. As the result of an ordinal Likert scale item by the median or mode can be summarized as positional parameters, but not by the arithmetic mean, as this presupposes a scale interval. see also ordinal scale level #

The aim of the construction of a Likert scale, however, is to make the construction of item and response options so that an approximation to the Äquidistanzforderung is achieved. The answer choices are therefore usually formulated symmetrically ( agree completely, somewhat agree, leaning neither from nor to agree, somewhat disagree, reject completely ). Furthermore, the perception of an equidistant scale is possibly supported by an illustration of a scale with the marked answer choices.

In practice, such Likert-type scales are used as interval scales. In the questionnaire and test practice ( easy availability of many parametric tests ) and test theoretical reasons (usually higher test strength in parametric methods ) is even adopted the metric scale level for pragmatic reasons.

See also: rating scale

A Likert scale is not a single individual, but of several items, which are often divided into scales and together form a questionnaire in general.

Even-numbered or odd-numbered scales?

There is an even number of response options as common as an odd number. The latter is used when a mean expression (neutral or " neither- nor " ) is useful. An even number forces the decision to one side. This practice is called Forced Choice.

Scale construction

It is customary to test a large number of items ( statements ) in a quantitative pilot study. Items are considered unsuitable if they show too few differences between respondents. A lack it is for example, if more than 80% of respondents agree with an item maximum ( ceiling effect ) or maximum to reject (floor effect). Such items are often sorted out.

You can sort more items due to low or negative correlation with the total test score to arrive at a possible one-dimensional scale (see Cronbach's alpha ).

Areas of application

Find use Likert scales in questionnaire surveys, particularly in empirical social, market and electoral research and psychology.

Example

Assume you want to measure the attitude to off-road cars. Based on theoretical considerations, among others, the following items are used:

• Item 1: Off -road cars are mainly driven by informers.
• Item 2: Women feel protected in off-road cars.

Response options ( assigned code ):

• Option 1: true ( 1), agree somewhat ( 2), part-part ( 3), rather does not (4) does not apply ( 5)
• Option 2: apply ( 1), agree somewhat ( 2), rather does not (3) does not apply ( 4)

A statement and selected on the response scale number thus provide an indicator of the attitude principal aim is to provide a consistent and clear-cut Final scale or Itemmenge, with a valid possible ( valid ) result for the investigated issue can be achieved.