09-01.2 samples and surveys and discrete and continuous

0901.2 Samples and Surveys and Discrete and Continuous Data.notebook March 07, 2014


Sometimes, these sampling methods result in biased samples.

A biased sample does not accurately represent the population. The data collected from biased samples is not reliable.

(pp 8)


Population Sample Possible BiasPeople in thelocal area

Up to 1500 peoplewho take the survey

Not all people arein the phone book

Identifying Biased SamplesA radio station manager chooses 1500 names from the local phone book to survey people about their listening habits.


An advice columnist asks her readers to write in with their opinions about how to hang the toilet paper on the roller.

Population Sample Possible BiasReaders of the column

Readers who write in

Only readers with strong opinions write in.


An eighth grade student council member polls classmates about a new school mascot.

Population Sample Possible Bias


The United States Census Bureauconducts a survey every ten years todetermine the population of the UnitedStates. The first U.S. census taken wasin 1790. Two hundred men rode onhorseback to count the number ofpeople in each household, and datawas recorded on small scraps of paper.This census cost the government just$45,000!Until 1960, the population survey wasconducted mostly door to door. At thattime, bureau officials realized that thismethod was inefficient because thepopulation was growing rapidly andbecoming more mobile and diverse.By 1980, 90% of the census was takenby mail.


(pp 8)


The percent of households with houseplants in Town A (42%) is close to the national percent. The percent of households in Town B (56%) is greater than the national percent.

Town A: # of households with plants total number of households =

Town B: # of households with plants total number of households =


Town A: # of households with pet fish total number of households =

Town B: # of households with pet fish total number of households=

The percent of households with pet fish in Town A (25%) is close to the national percent. The percent of households in Town B (55%) is greater than the national percent.


Learn to identify sampling methods and to recognize biased samples and show understanding through class work.

Students will

Learning Objective


Discrete and Continuous QuantitiesComparison between a continuous and discrete system

(pp 10)


Discrete quantities you can count ex: number of people who enter the library

Continuous quantities you can measure ex: temperature of water as it is heated


Identify each quantity as continuous or discrete.

the water level in a sink as it is being filled

the speed of a car driven from your home to the mall

the number of stars you can see

a person's weight

attendance at a football game

population of Ohio

continuous discrete

continuous

continuous

discrete

continuous

discretediscrete


Complete(pp 11) #115page 464


Population: deli customers; sample: Sunday’s customers; possible bias: the sample does not include weekday customers.

Population: people who attend the team’s games; sample: people other than season ticket holders

attend baseball games.


Every fifth name is called.

The sample is conveniently in the hair salon.

The teacher draws a question at random from the box.

The visitors to the web site have chosen to be in the sample.

Each study group is a randomly chosen subgroup; one person is selected at random from each one.


Population: students;sample: students who buy the entrée; possible bias: the student who buy the entrée may be the people who like the food in the cafeteria.

Population: city residents; sample: people attending the city council meeting; possible bias: most citizens do not attend city council meetings.

Population: trees; sample: trees along the river;possible bias: the trees sampled have a better

source of water than the others.

09-01.2 samples and surveys and discrete and continuous

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