sections 2.3 – 2.6 recap
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Sections 2.3 – 2.6 Recap. Unit Test on Tuesday, October 2, 2012. 2.3 Sampling Techniques. Scenario : A sample of young adults were surveyed regarding their diets. If the sample consists of young adults, then who is the population of this study?. - PowerPoint PPT PresentationTRANSCRIPT
Sections 2.3 – 2.6
RecapUnit Test on
Tuesday, October 2, 2012
2.3 Sampling Techniques
Scenario:
A sample of young adults were surveyed regarding their diets.
If the sample consists of young adults, then who is the population of this study?
Scenario:
A sociology professor talks to every 9th elementary school student walking into the local library about their reading skills. If he interviewed 34 people, what is the population size?
A sociology professor talks to every 9th elementary school student walking into the local library about their reading skills. If he interviewed 34 people, what is the population size?
interval = pop. size / sample size
Re-arrange it to get
pop. size = interval x sample size = 9 x 34 = 306 elem. school students
Was that an example of systematic sampling or stratified
sampling?
Sample Types
Sample
Simple random sample
Systematic sample
Stratified sample
Sample Types Cluster sample –
Multi-stage sample
Voluntary-response sample
Convenience sample
Sample Types Cluster sample - the total population is
divided into groups (or clusters) and a simple random sample of the groups is selected.
Multi-stage sample
Voluntary-response sample
Convenience sample
Sample Types Cluster sample - the total population is
divided into groups (or clusters) and a simple random sample of the groups is selected. *My drawing on the white board was not a definition, it was only describing the textbook’s fast-food chain example.
Multi-stage sample -
Voluntary-response sample
Convenience sample
Sample Types Cluster sample - the total population is
divided into groups (or clusters) and a simple random sample of the groups is selected. *My drawing on the white board was not a definition, it was only describing the textbook’s fast-food chain example.
Multi-stage sample – several levels of random sampling
Voluntary-response sample –
Convenience sample
Sample Types Cluster sample - the total population is
divided into groups (or clusters) and a simple random sample of the groups is selected. *My drawing on the white board was not a definition, it was only describing the textbook’s fast-food chain example.
Multi-stage sample – several levels of ran. sampling
Voluntary-response sample – researcher invites any member of population into survey
Convenience sample
Sample Types Cluster sample - the total population is
divided into groups (or clusters) and a simple random sample of the groups is selected. *My drawing on the white board was not a definition, it was only describing the textbook’s fast-food chain example.
Multi-stage sample – several levels of ran. sampling
Voluntary-response sample – researcher invites any member of population into survey
Convenience sample
Sample Types Cluster sample - the total population is divided
into groups (or clusters) and a simple random sample of the groups is selected. *My drawing on the white board was not a definition, it was only describing the textbook’s fast-food chain example.
Multi-stage sample – several levels of ran. sampling
Voluntary-response sample – researcher invites any member of population into survey
Convenience sample - sample selected but it’s easily accessible
Question A community centre chooses 15 of its
members and asks them to have each member of their families complete a short questionnaire.
A) What type of sample is the community centre using?
Question A community centre chooses 15 of its
members and asks them to have each member of their families complete a short questionnaire.
A) What type of sample is the community centre using?
Answer: Cluster Sample
Question A community centre chooses 15 of its
members and asks them to have each member of their families complete a short questionnaire.
B) Are the 15 community-centre members a random sample of the community?
Question A community centre chooses 15 of its members
and asks them to have each member of their families complete a short questionnaire.
B) Are the 15 community-centre members a random sample of the community?
Answer: No, not every member has an equal chance of being selected
Question A community centre chooses 15 of its
members and asks them to have each member of their families complete a short questionnaire.
C) To what extent are the family members randomly chosen?
Question
A community centre chooses 15 of its members and asks them to have each member of their families complete a short questionnaire.
C) To what extent are the family members randomly chosen?
Answer: to the same extent as the member of the community was selected
2.4 Bias in Surveys Sampling Bias
Non-response Bias
Measurement Bias
Response Bias
2.4 Bias in Surveys Sampling Bias – sample doesn’t rep. population
Non-response Bias – groups under-represented in survey b/c they chose not to participate
Measurement Bias – data collection method misestimates population characteristics
Response Bias – false/misleading answers given because of sensitive survey questions
Intentional bias –
Unintentional bias –
Leading questions –
Loaded questions -
Intentional bias – used to manipulate stats in favour of a certain point of view
Unintentional bias – can be introduced if sampling and data collection methods are not chosen carefully
Leading questions – can give suggested answers which causes a bias
Loaded questions – contains wording or information intended to influence respondents’ answers
Any bias below?
Can the proposed record level of
healthcare expenditures be justified in
view of the enormous deficits facing the
Canadian people and the pressing social
needs that are currently unmet?
2.5 Measure of Central Tendency
What does the above mean?
2.5 Measure of Central Tendency
What does the above mean?
values around which a set of data tends
to cluster
What is the difference between and ?
What is the difference between and ? refers to mean of population
refers to mean of sample
What is the difference between and ?
Hand back quizzes & … Exercise: Calculate mean quiz mark with
proper weights
Knowledge/Understanding 40%
Application 30%
Communication 10%
Thinking 20%
Grade 10 Exam Question on Determining the Centroid
Grade 10 Exam Question on Determining the Centroid
x mean = (1+3+5)/3 = 3
y mean = (2+4+0)/3= 2
centroid = (3, 2)
You can calculate x mean, y mean & z mean to get centroid of 3D objects
Grade 10 breaks down when weights are applied. Consider bottom right vertex mass = 2.2 kg top vertex mass = 5.7 kg left vertex mass = 0.2 kg Determine the center of the mass
x mean = [1(0.2)+3(5.7)+5(2.2)] / (0.2 + 5.7 + 2.2) = 3.5
y mean = [2(0.2)+4(5.7)+0(2.2)] / (0.2 + 5.7 + 2.2) = 2.9
Grade 10 breaks down when weights are applied. Consider bottom right vertex mass = 2.2 kg top vertex mass = 5.7 kg left vertex mass = 0.2 kg Determine the center of the mass
2.6 Measures of Spread
We’ll do this tomorrow
Review Questions Q #1, 5, 6, 7, 9, 11, 14
Page 151-152