Page 86 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

Customer Survey Design, Administration, and Analysis 67

The disadvantages of closed-ended questions include
1. Closed-ended questions compel respondents to choose the closest rep-
resentation of their actual response on the list of prespecified answers,
which may deviate from their true opinions.
2. When respondents are unsure of what is the best answer, they may
choose a random answer, which will lead to errors.

Level of Measurements in Closed-Ended Questions
Before being analyzed, the survey data should be organized as variables. A
variable is a specific characteristic of the population, such as age, sex,
preference, and rating. Depending on the design of the questions and answers,
the variables used in the survey have different measurement properties, referred
to as levels of measurement or measurement scales. The commonly used meas-
urement scales include nominal, ordinal, and interval. In survey design, there
is a specially designed interval scale called the Likert scale. We are going to
discuss these in detail.

Nominal Scale
The nominal level of measurement simply places the survey answers into
categories. For example, a variable such as political party preference in the
United States can be categorized as three classes, Democrat, Republican, or
Independent. In nominal scale, survey data can be placed into categories
and their frequency of occurrences counted. There is no ranking or ordering
of the categories.

Ordinal Scale
The ordinal level of measurement goes one step beyond the nominal scale;
it ranks the categories by a certain criterion. For example, the education
levels of people can be classified into the following categories: high
school graduate or lower, two-year college degree, bachelor’s degree,
master’s degree, and Ph.D. degree. Clearly, we can rank these education
levels; a Ph.D. is certainly higher than a master’s, for example, but it is
difficult to define a numerical difference between these educational
achievements.

The Interval Scale
The interval level of measurement gives the greatest amount of information
about the variables. It labels, orders, and uses numerical units of measure to
indicate the exact value of each category. For example, variables such as
income, age, and weight are in interval scales.