To get valid results survey samples must be chosen very carefully An unbiased sample is selected so that it accurately represents the entire population Two ways to pick an unbiased sample are on the ID: 622599
Download Presentation The PPT/PDF document "Biased vs. Unbiased Samples" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Biased vs. Unbiased SamplesSlide2
To get valid results, survey samples must be chosen very carefully. An unbiased sample is selected so that it accurately represents the entire population. Two ways to pick an unbiased sample are on the
next
two slides.Slide3
Unbiased Samples
Simple Random Sample – each item or person in the population is as likely to be chosen as any other
Example: Each student’s name is written on a piece of paper. The names are placed in a bowl, and names are picked without looking.Slide4
Unbiased Samples
Systematic Random Sample – the items or people are selected according to a specific time or time interval
Example: Every 20
th
person is chosen from an alphabetical list of all students attending a schoolSlide5
In a biased sample, one or more parts of the population are favored over others. Two ways to pick a biased sample are listed on the next slide.Slide6
Biased Samples
Convenience Sample – a convenience sample consists of members of a population that are easily accessed
Example: To represent all the students attending a school, the principal surveys the students in one math classSlide7
Biased Samples
Voluntary Response Sample – a voluntary response sample involves only those who want to participate in the sampling
Example: Students at a school who wish to express their opinions complete an online surveySlide8
Biased or Unbiased?
A random sample of students at a middle school shows that 10 students prefer listening to rock, 15 prefer hip hop, and 25 prefer no music while they exercise. In can be concluded that half the students prefer no music when they exercise.Slide9
Biased or Unbiased?
Every tenth person who walks into a department store is surveyed to determine his or her music preference. Out of the 150 customers, 70 stated that they prefer rock music. The manager concludes that about half of all customers prefer rock music.Slide10
Biased or Unbiased?
The customers of a music store are surveyed to determine their favorite leisure time activity. The results are shown in the table. The store manager concludes that most people prefer to listen to music in their free time.
Playing Sports
6%
Listening to Music
85%
Other
9%Slide11
Biased or Unbiased?
A radio station asks its listeners to indicate their preference for one of two candidates in an upcoming election. 72% of the listeners who responded prefer candidate A, so the radio station announced that candidate A would win the election. Is the conclusion valid? Explain.Slide12
Biased or Unbiased?
Every tenth student who walked in the cafeteria was surveyed to determine his/her favorite lunch. Out of 40 students, 19 students stated that they liked hamburgers best. The staff concluded that about 50% of the students prefer hamburgers. Is the conclusion valid? Explain.