Is a Likert Scale a Ratio Scale?

When it comes to measuring attitudes or opinions, the Likert scale is a popular choice among researchers and businesses alike. But the question often arises: is a Likert scale a ratio scale? This article delves into the intricacies of these measurement scales to provide a clear understanding of their differences and similarities.

The Likert scale, named after its creator, Rensis Likert, is a type of rating scale commonly used in survey research. It consists of a statement or question followed by a series of response options, typically ranging from 'Strongly Agree' to 'Strongly Disagree'. On the other hand, a ratio scale is a type of measurement scale where the intervals between data points are equal, and there is a true zero point.

Understanding Ratio Scales

Ratio scales are used to measure quantities and have four key properties: they have a true zero point, the intervals between data points are equal, they are ordered, and they have a meaningful zero point. Examples of ratio scales include temperature in Celsius or Fahrenheit, weight, and time.

One of the most significant aspects of ratio scales is their ability to perform arithmetic operations. Since the intervals are equal and there's a true zero point, you can meaningfully add, subtract, multiply, and divide the data. This makes ratio scales highly versatile and useful in many fields.

Interval and Ratio Scales: A Close Relationship

Interval scales are a subset of ratio scales. They also have equal intervals between data points but lack a true zero point. Examples include the Celsius scale (which has a zero point but not a true zero point) and IQ tests. While you can perform arithmetic operations with interval scales, the results may not be meaningful due to the absence of a true zero point.

For instance, while you can say that a person with an IQ of 120 is smarter than someone with an IQ of 100, you cannot say that they are twice as intelligent. This is because IQ tests do not have a true zero point, and the zero point on the scale is arbitrary.

Ordinal and Interval/Ratio Scales: A World Apart

Ordinal scales, on the other hand, are a completely different story. They only have an ordering or ranking of data points. For example, a satisfaction scale with options like 'Very Satisfied', 'Somewhat Satisfied', 'Neutral', 'Somewhat Dissatisfied', and 'Very Dissatisfied' is an ordinal scale. You can order these responses, but you cannot say that the difference between 'Very Satisfied' and 'Somewhat Satisfied' is the same as the difference between 'Neutral' and 'Somewhat Dissatisfied'.

Moreover, you cannot perform arithmetic operations with ordinal data. You cannot add or subtract 'Very Satisfied' from 'Somewhat Dissatisfied' and expect to get a meaningful result.

Likert Scales: A Closer Look

Now that we've established the properties of ratio scales, let's examine the Likert scale more closely. A typical Likert scale has five response options, ranging from 'Strongly Agree' to 'Strongly Disagree'. Some variations may have more or fewer options, but the principle remains the same.

The response options on a Likert scale are ordinal, meaning they can be ranked. However, they are not interval or ratio scales. The intervals between the response options are not equal, and there is no true zero point. For instance, the difference between 'Agree' and 'Strongly Agree' is not necessarily the same as the difference between 'Neutral' and 'Disagree'.

The Issue of Neutrality

One of the main criticisms of the Likert scale is its lack of a true neutral point. While some Likert scales include a 'Neutral' option, this does not necessarily mean that the scale is now interval or ratio. The 'Neutral' point is still arbitrary, and the intervals between the other response options remain unequal.

Moreover, the inclusion of a 'Neutral' option can sometimes lead to respondents using it as a default or 'easy' response, which can skew the results of the survey.

Likert Scales and Arithmetic Operations

Due to the unequal intervals and lack of a true zero point, you cannot perform arithmetic operations with Likert scale data. While you can calculate means, medians, and modes, these statistics do not provide the same level of information as they would with ratio scale data.

For example, if you calculate the mean of a set of Likert scale responses, you cannot say that the result represents the 'average' opinion of the respondents. You can only say that it represents the 'central tendency' of their responses.

In conclusion, while Likert scales are powerful tools for measuring attitudes and opinions, they are not ratio scales. Understanding the difference between these two types of measurement scales is crucial for interpreting and analyzing data correctly. By recognizing the limitations of Likert scales, researchers and businesses can make more informed decisions about how to use and interpret their data. So, the next time you encounter a Likert scale, remember that while it's a useful tool, it's not a ratio scale, and its data should be treated accordingly."