This document discusses populations, samples, and sample bias. It defines a population as the whole group of interest, while a sample is a subset of the population. Taking a random sample is important to avoid bias, where every member has an equal chance of being selected. The document provides examples of populations like all 7th graders at a school, and samples like surveying a classroom. It explains how non-random samples from convenience can produce biased results, while random sampling helps ensure the sample accurately represents the overall population. Students are assigned to collect data from a sample on a topic and population, and analyze if their sample showed any bias.

1. Populations and Samples
Made for 7th grade Mathematics
By SaulVillavicencio

2. Objectives
▪ Learn the difference between population and sample
▪ Learn what sample bias is
▪ Learn how to avoid sample bias
▪ Be able to gather data about a population using a sample

3. Introduction
▪ In math we often have to collect data on a group often called a
population
▪ We could ask the whole population
– That would be okay if you have a small group like a classroom
– Can be impractical if your group is the world or even a whole school
▪ We often just ask a part of the group, called a sample, to get the
general response of the population
▪ But if we ask the wrong people our sample can be bias

4. What is a Population?
▪ A population is the whole group which you are interested in finding
some information about
▪ What if I wanted to find the average height of all the 7th graders at
Brea Junior High School?
– My population would be all the 7th graders, not the entire school

5. Lets Give it a try
▪ For our data set our population
will be the entire classroom
▪ Question:Which of the
following the classes favorite
sport: baseball, soccer,
basketball, football, or hockey?
▪ What can we infer from this
graph?
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Baseball Soccer Basketball Footballl Hockey
Students’ Favorite Sport
Students

6. What is a Sample?
▪ A sample is a subset from the population
▪ We use a sample in cases where getting information about the whole
population may be impractical
▪ What if we wanted to find the average height of the students at Brea
Junior High School?
– We could ask everyone but that could take too long and would be impractical
– We also could also take a sample and have them represent the population

7. Lets Give it a Try
▪ For our data our population will
be the whole 7th grade class
▪ Our sample is this classroom
▪ Question:What is the school’s
favorite academic subject?
▪ Can we truly say that our
sample represents the
population?
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Math Science History Language Arts
Students’ Favorite Subject
Student

8. Sample Bias
▪ Our previous sample would be
bias
▪ It was a convenience sample
– You’re already here so it was easy
to pick you
▪ Also since I was asking it you
might be more inclined to say
math

9. Random Sample
▪ We need to get a random
sample so that it can be
representative of the
population.
▪ In a random sample every
sample has an equal chance of
getting picked

10. How Would We Get a Random Sample?
▪ We could go around asking students randomly
– Some might just ask their friends
– Some might not answer
▪ We could randomly draw our samples from a computer program
▪ Can you think of any other ways to get a random sample?

11. Assignment
▪ Get in a group of 2-4 people
▪ Pick a topic you want some information on
▪ Pick a population for your topic
▪ Find the data for that population from a sample
▪ Make a graph of the data
▪ Write up a report about the data you got
▪ Write about if this sample is bias or not