Page 194 - Math Course 3 (Book 2)

Sampling and Bias
Mo. 12

Lesson 4 simple random sample

A simple random sample is a sample that is as
equally likely to be chosen as any other sample
from the population.
KEY CONCEPTS:
The 26 students in a class are each assigned a
1. Identify various sampling techniques. different number from 1 to 26. Then three of the
2. Recognize a biased sample. 26 numbers are picked at random.

stratified random sample

In a stratified random sample, the population is first
MO. 12 - L4a divided into similar, non overlapping groups.
A sample is then selected from each group.

Sampling Techniques The students in a school are divided into grade
levels: freshmen, sophomores, juniors, and
seniors. Then two students are randomly
selected from each group of students.
Vocabulary A-Z

Let us learn some vocabulary systematic random sample
In a systematic random sample, the items are se-
lected according to a specified time or item interval.

Every 2 minutes, a person is searched at the
Population airport. Or every twentieth person is searched at
the airport.

Key Concept
Sample

Random Samples

sample Simple random sample
A sample is some portion of a larger group.
Definition Examples
A simple random The 26 students in a
sample is a sample that class are each assigned
population is as likely to be chosen a different number from
A sample is some portion of a larger group, called as any other sample 1 to 26. Then three of
the population, selected to represent that group. from the the 26 numbers are
population. picked at random.

random sample Stratified random sample
A random sample of a population is selected so
that it is representative of the entire population. Definition Examples
The sample is chosen without any preference. In a stratified random The students in a school
sample, the population are divided into grade
is first divided into levels: freshmen,
similar, non overlapping sophomores, juniors,
groups. A sample is and senior. Then two
then selected from each students are randomly
group. selected from each
group of students.

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