STATISTICS
(SAMPLING TECHNIQUES)
When conducting a survey, it is important to choose the right
questions to ask and to select the appropriate group to survey.
Therefore, before a survey is designed, the target group for the
survey must be identified.
In many situations, it is not practical or possible to survey an entire
population, so a representative sample of the population is selected.
population:
all individuals or items that belong to a group
being studied (the target group)
ex.
sample:
a group of individuals or items that are representative
of the population from which they are taken
ex.
bias:
a survey contains bias if it does not reflect the population
Causes:
1.
2.
3.
Example 1:
Barney wants to know which band Ontario high school students
think is best. Barney’s friend Fred goes to a different school, so
they each survey students at their own school. Barney uses the
completed surveys from both schools to draw conclusions.
a)
Identify the population and sample.
b)
Is the sample representative of the population? If not,
suggest how the sample could be improved.
Unit 8 Lesson 1
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SAMPLING TECHNIQUES
Simple Random Sample
Stratified Random Sample
Voluntary-Response Sample
Cluster Sample
Convenience Sample
Systematic Sample
Example 2:
 each member of the population has an equal chance
of being selected
Ex.
 the population is divided into subgroups and a
random sample is selected from each subgroup in
proportion to its size in the population
Ex.
 the sample contains members of the population who
have chosen to respond to the survey
Ex.
 the population is divided into clusters and every
member of certain clusters respond
Ex.
 the sample contains those members of the population
from which data is most easily collected
Ex.
 every nth member of the population is selected
Ex.
Determine the best sampling technique for each survey. Identify
any problems with using the sampling technique.
a)
The school newspaper wants to determine which presidential candidate in the
upcoming student council elections is supported by the majority of students.
b)
A light bulb manufacturer wants to determine the
lifespan of a certain type of light bulb, in hours.
c)
The PTA wants to determine the average number of
hours per week that students spend on homework.
d)
The producers of “ROCK IDOL” want to determine
who should be the next rock idol.
HOMEWORK:
p.106–108 #1–4 , 7–9
Unit 8 Lesson 1
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