6'6 Analyze Surveys

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6.6 Analyze Surveys Samples
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Vocabulary

• A survey is a study of one or more
  characteristics of a group.
• The entire group you want information about is
  called a population.
• A sample is a part of the population.
• In a random sample, every member of the
  population has an equal chance of being selected.

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• In a stratified random sample, the population is
  divided into distinct groups. Members are
  selected at random from each group.
• In a systematic sample, a rule is used to select
  members of the population.
• In a convenience sample, only members of the
  population who are easily accessible are
  selected.
• In a self-selected sample, members of the
  population select themselves by volunteering.

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• A representative sample is a sample that
  accurately reflects the characteristics of a
  population.
• A biased sample is a sample that is not
  representative of the population.
• A question that encourages a particular response
  is a biased question.

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Sampling Method How Members Are Chosen

• Random
• Systematic
• Stratified
• Convenience
• Self-Selected

• By Chance
• Rule or formula
• Random from subgroups
• Easy to reach
• Volunteers

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Identify the sampling method used.

• In a county survey, Democratic party members
  whose names begin with the letter D are chosen.
• systematic

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Identify the sampling method used.

• Customers at a bank are asked to take a survey
  about their financial practices.
• convenience

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Identify the sampling method used.

• A cell phone company randomly chooses customers
  to survey about its service.
• random

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Identify the sampling method used.

• A newspaper columnist asks readers to write in
  with their ten favorite restaurants.
• Self-selected

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Identify the sampling method used.

• A high school randomly chooses three classes from
  each grade and then draws three random names from
  each class to poll about lunch menus.
• stratified

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Give a reason why the sample could be biased.

• A company wants to find out how customers rate
  their products. They ask people who visit the
  companys web site to rate their products.
• Many people who use the product will not visit
  the web site.

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Give a reason why the sample could be biased.

• A teacher polls all of the students who are in
  detention on Friday about their opinions on the
  amount of homework students should have each
  night.
• Students in detention may be the least likely to
  do homework.

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Explain why the question is biased and rewrite it
so that it is not.

• Dont you think that it is better for the school
  to offer two lunch choices and salad than to
  offer one choice and salad?
• The question suggest that it is better to offer
  two choices than to offer one.
• Do you think the school should offer two lunch
  choices and salad or one choice and salad?

14
Read the description of the survey and identify
the population, the sample, any possible bias,
and the sampling method used.

• A car dealership wants to know how people who
  visited the dealership feel about the dealership
  and the sales people. They survey every 5th
  person who buys a car.

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• Population people who visit the dealership
• Sample every 5th buyer
• Possible bias not including those who visited
  but did not buy a car
• Sampling method systematic