As discussed in a previous issue a

As discussed in a previous issue a survey
involves directly collecting information
from people (or sometimes organisations)
whom we are interested in.1 The
types of information will take account of
the people’s or organisations’ level of
knowledge, attitude, personalities, beliefs,
or preferences. Questionnaires are widely
used to collect such information. Well
designed questionnaires are highly structured
to allow the same types of information
to be collected from a large number
of people in the same way and for data to
be analysed quantitatively and systematically.
Questionnaires are best used for
collecting factual data and appropriate
questionnaire design is essential to ensure
that we obtain valid responses to our
questions.
Objectives in designing
questionnaires
There are two main objectives in designing
a questionnaire:
l To maximise the proportion of subjects
answering our questionnaire—that is,
the response rate.
l To obtain accurate relevant information
for our survey.
To maximise our response rate, we have
to consider carefully how we administer
the questionnaire, establish rapport,
explain the purpose of the survey, and
remind those who have not responded.
The length of the questionnaire should be
appropriate. In order to obtain accurate
relevant information, we have to give some
thought to what questions we ask, how we
ask them, the order we ask them in, and the
general layout of the questionnaire.
Deciding what to ask
As discussed in last month’s issue, there
are three potential types of information:
l Information we are primarily interested
in—that is, dependent variables.
l Information which might explain the
dependent variables—that is, independent
variables.
l Other factors related to both dependent
and independent factors which may
distort the results and have to be
adjusted for—that is, confounding variables.
Let us take as an example a national
survey to find out students’ factors predicting
the level of certain knowledge,
skills, and attitudes at the end of their
undergraduate medical course. The
dependent factors include the students’
level of relevant knowledge, skills, and
attitudes. The independent factors might
include students’ learning styles, GCSE
and A level grades, socioeconomic status,
ethnicity, etc. Confounding variables
might include the types and quality of
teaching in each medical school.
Sometimes, additional questions are
used to detect the consistency of the subject’s
responses. For example, there may
be a tendency for some to tick either
“agree” or “disagree” to all the questions.
Additional contradictory statements may
be used to detect such tendencies.
Wording of individual questions
The way questions are phrased is important
and there are some general rules for
constructing good questions in a questionnaire.
Use short and simple sentences
Short, simple sentences are generally less
confusing and ambiguous than long,
complex ones. As a rule of thumb, most
sentences should contain one or two
clauses. Sentences with more than three
clauses should be rephrased.
Ask for only one piece of information at
a time
For example, “Please rate the lecture in
terms of its content and presentation”
asks for two pieces of information at the
same time. It should be divided into two
parts: “Please rate the lecture in terms of
(a) its content, (b) its presentation.”
Avoid negatives if possible
Negatives should be used only sparingly.
For example, instead of asking students
whether they agree with the statement,