Advanced Algebra
Name _________________________________
Statistics
Period ______ Date ______________________
Population vs. Sample Notes
Population vs. Sample
Data:
Definitions: POPULATION AND SAMPLE
The entire group of individuals that we want information about is called the ________________.
When it is too costly or impractical to survey everyone in the population, you can take a sample.
A __________ is a part or subgroup of the population that we actually examine in order to gather
information. The sample data represents the population well enough that you can draw conclusions or
inferences about the population by knowing information only about the sample.
Population: All the cats in the world!
Sample: The cats at my house. Obviously not
representative of the population.
Example 1: For each scenario below, decide if a population or sample was used.
a) The age of all High School principals
b) A survey of 300 students out of 1000 Liberty Students.
c) The color of hair of every 4th girl that leaves a salon
Example 2: Identify the target population and sample used in each scenario:
a) A survey of 1,000 U.S. adults found that 59% think buying a home is the best investment a family can
make. (source: Rasmussen Reports)
b) A study of 33,043 infants in Italy was conducted to find a link between a heart rhythm abnormality and
sudden infant death syndrome. (source: New England Journal of Medicine)
Types of Samples and Representative vs. Non-Representative
If you're capable of doing a study on the ___________ population then that's called a ____________. Otherwise,
in order to have a meaningful representation of the population you need to be careful about how you pick
your sample.
The sample needs to be _______________ of our population, not just a few or biased subgroup.__
systematic favoring of one outcome.
____ is a
__________________________: Every possible sample of the same size has the same chance of being selected.
This is done by assigning a number to each member of the population and then using a random number
generator (table or program) to pick who is selected.
____________________: Every member is assigned a number and every 3rd or 5th or 100th person is selected.
____________________: A sample is taken from whomever is most convenient or available. --Leads to biased
studies due to Non-Representative samples.
____________________: Members of the population are divided into subsets called strata. Members of the same
strata share similar characteristics. A sample is then randomly selected from each strata.
__________________: People volunteer to be in the sample by choosing to be take part in the study. Usually
people with the strongest opinions respond to surveys. --Leads to biased studies due to NonRepresentative samples.
Example 3: For each problem below, write 1-2 sentences describing the type of sampling used and
an explanation if the method would lead to a representative or non-representative sample.
a) The names of 40 contestants are written on 40 cards. The cards are placed in a bag, and three names
are drawn from the bag to announce winners
b) To avoid working late, the quality control manager inspects the last 50 items produced that day.
c) To ensure customer satisfaction, every 20th phone call received by customer service will be
monitored.
d) Using student ID numbers, you randomly select 25 students from each class; Freshmen, Sophomores,
Juniors, and Seniors.
e) To find out whether you enjoyed a book you just read, Amazon.com asks you to complete a survey and
rate the book when you've finished.