Transcript How to Make a Valid and Unbiased Survey

How to Make a Valid
and Unbiased Survey
First Step
• Brainstorm…
– What is the topic of your survey
– What is the objective, or what
information are you trying to obtain
– Make sure your questions specifically
address the objectives you are trying to
learn, for ex: If you are trying to make
a survey on drug usage for high school
students, you might ask, “Have you ever
tried Marijuana?” and if so, “How often
do you smoke marijuana?”
Who is the audience?
• If you are going to ask a small group
you can ask everybody (called a
Census)
• If you want to survey a large group,
you may not be able to ask everybody
so you should ask a sample of the
population (this is called Sampling)
•
•
What does bias have to
do
with
it?
If you are Sampling you should be careful who you ask, for example:
– If you only ask people who look friendly, you will only know what
friendly people think!
– If you went to the swimming pool and asked people "Can you
swim?" you will get a biased answer ... maybe even 100% will say
"Yes"
The surveys where people are asked to ring a number to vote are not
very accurate, because only certain types of people actually ring up!
So be careful not to bias your survey.
– Example: You want to know the favorite colors for people at your
school, but don't have the time to ask everyone.
– Solution: Choose 50 people at random:
– stand at the gate and choose "the next person to arrive" each
time
– or choose people randomly from a list and then go and find them!
– or you could choose every 5th person
Your results will hopefully be nearly as good as
if you asked everyone.
Now that you have your
audience, Create the survey…
• Types of Questions
• A survey question can be:
• Open-ended (the person can answer in any way they want),
or
• Closed-ended (the person chooses from one of several
options)
• Closed ended questions are much easier to total up later on,
but may stop people giving an answer they really want.
• Example: "What is your favorite color?"
• Open-ended: Someone may answer "dark fuchsia", in which
case you will need to have a category "dark fuchsia" in your
results.
• Closed-ended: With a choice of only 12 colors your work will
be easier, but they may not be able to pick their exact
favorite color.
Question Sequence
• It is important that the questions don't "lead" people to the
answer
• Example: people may say "yes" to donate money if you ask the
questions this way
– Do you love nature? Will you donate money to help the river?
• But probably will say "no" if you ask the questions this way:
– Is lack of money a problem for you? Will you donate money to help
the river?
• To avoid this kind of thing, try to have your questions go:
•
– from the least sensitive to the most sensitive
– from the more general to the more specific
– from questions about facts to questions about opinions
Go through your questions and put them in the best sequence
possible
– Example: I will ask people how often they visit the river (a fact)
before I ask them what they feel about pollution (an opinion)
– I will ask people their general feelings about the environment
before I ask them their feelings about the river.
Make your questions Neutral
• Your questions should also be neutral ... allowing
the person to think their own thoughts about the
question.
• In the example before I had the question "Do you
love nature?" ... that is a bad question because it
is almost forcing the person to say "Yes, of
course."
• Try rewording it to be more neutral, for example:
– Example: "How important is the natural environment to
you?"
• Not Important
• Some Importance
• Very Important
Tally up the data or the
results….
• Tally the Results
• Now you have finished asking questions it
is time to tally the results.
• By "tally" I mean add up. This usually
involves lots of paperwork and computer
work (spreadsheets are useful!)
• Example: For "favorite colors of my class"
you can simply write tally marks like this
(every fifth mark crosses the previous 4
marks, so you can easily see groups of 5):
The Results….
• Look at your survey results for trends and
patterns.
• What conclusions can you draw from the
survey results?
• Write a conclusion, and include any tables
or graphs that help you present your
survey results
Ways to present your results
• Tables
– Sometimes, you can simply report the information
in a table.
– A table is a very simple way to show others the
results. A table should have a title, so those
looking at it understand what it shows:
• Statistics
– You can also summarize the results using
statistics, such as mean or standard deviation
– Example: you have lots of information about how
long it takes people to get to school but it may be
simpler just to present a summary such as:
• Shortest Journey: 3 minutes
Average Journey: 22 minutes
Longest Journey: 58 minutes
•
Graphs
– Nothing makes a report look better than a nice graph or chart
– There are many different types of graphs. Three of the most common
are:
• Line Graph - Used to show information that is somehow connected
(such as change over time)
• Pie Chart - Used most often to show survey data that is to be reported
in percentages.
• People's Comments
– If people have given their opinions or
comments in the survey, you can present
the more interesting ones:
– Example: In response to the question
"How can we best clean up the river?"
we received these interesting replies:
• "The government has a special fund for this"
• "The local gardening group has seedlings you
could plant"
Resources
• http://www.microsoft.com/education
/DesignSurvey.aspx?pf=true
• http://www.mathsisfun.com/data/sur
vey-conducting.html