Page 196 - Math Course 3 (Book 2)
P. 196

Sampling and Bias





         MO. 12 - L4b                                       Key Concept


          Recognizing a Biased Sample
                                                            Biased Samples

                                                            Type             Convenience sample
                     Vocabulary A-Z                         Definition  A convenience sample includes

                     Let us learn some vocabulary                     members of a population who are
                                                                      easily accessed.
                                                            Example   To check spoilage, a produce worker
         biased sample                                                selects 10 apples from the top of the
                                                                      bin. The 10 apples are unlikely to
         Random samples are unbiased. In a biased sample,             represents all of the apples in the bin.
         one or more parts of a population are favored over
         others.                                            Type          Voluntary Response sample

           Every 2 minutes, an Asian person is searched at   Definition  A voluntary response sample involves
                           the airport.                               only those who want to participate in
                                                                      the sampling.

                                                            Example   A radio call-in show record that 75% of
                                                                      its 40 callers voiced negative opinions
                                                                      about a local football team. Those 40
                                                                      callers are unlikely to represents the
                                                                      entire local population.
            Biased Sample          Unbiased Sample
                                                                      Volunteer caller are more likely to have
                                                                      strong opinions and are typically more
                                                                      negative than the entire population.
         convenience sample
         A convenience sample includes members of a
         population who are easily accessed.
                                                                         Let’s Begin
            To check spoilage, a produce
           worker selects 10 apples from
          the top of the bin. The 10 apples
           are unlikely to represents all of               Identify Sample as Biased or Unbiased
               the apples in the bin.
                                                              Example


         voluntary response sample
         A voluntary response sample involves only those    STUDENT COUNCIL
         who want to participate in the sampling.           The student council surveys the students in one
                                                            classroom to decide the theme for the spring
            A radio call-in show record that 75% of its 40   dance.
           callers voiced negative opinions about a local
           football team. Those 40 callers are unlikely to   Identify the sample as biased or unbiased. Explain
               represents the entire local population.      your reasoning.

           Volunteer caller are more likely to have strong   The sample includes only students in one class-
          opinions and are typically more negative than the   room.
                        entire population.


                                                              Answer          The sample is biased.




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