Random or No Random
Estimating Population Size
Vocabulary
Mics
Biased Or Fair
100
Joe wants to know the height of the average 7th grade student at Holcomb Bridge Middle School. He creates a sample using only members of the basketball team. Random or Not random
Not Random because Joe only surveyed the basketball team.
100
John is trying to estimate the size of the ape population in Spain. He randomly catches 37 apes and marks them with paint. He then releases them back into the jungle. The following day, he observes 250 apes total and only 10 of those apes were marked with paint. Estimate the total population.
925 apes
100
Small portion of a population
Sample
100
What is a box plot?
A line with a box through it
100
An 8th grade student council member wants to know what students would like as their new school mascot. He randomly selects 40 students to ask. Is this a biased or unbiased sample?
Fair; He RANDOMLY selected the students to ask.
200
A principal wants to determine, on average, how long a 7th grade student studies per night. He creates a sample using only students who have all A's. Random or not random?
Not Random. Principal only surveys students with A's.
200
The government of Mexico declared blue sharks an endangered species. They put tags on 36 blue sharks and release them. Later, they corral 130 blue sharks and find that 20 of them have tags. Estimate the population size.
234 blue sharks
200
The whole group being surveyed
Population
200
What is a dot plot?
It is a chart with dots that holds data.
200
At a Math teacher convention, Sam surveys the teachers to find out their favorite subject in school. Is this a biased or unbiased sample?
Biased; Sam is asking ONLY Math teachers.
300
The Holcomb Bridge Middle School Booster Club has $1000 to give to one of the school's clubs (i.e. band, the basketball team, etc.). They decide to take a survey to determine who they will give the money to. They only survey students in a band class. Random or Not random?
Not random. Only surveyed students in band.
300
You are part of an international project on a Pacific Island to study brown snakes. You and your team capture 750 snakes the first day you are there and tag them. The next day, you recapture 50 snakes and find that 30 of them have tags. Estimate the population size.
1250 brown snakes
300
Each person in the population has an equal chance of being included in a survey
Random Sample
300
What is the difference between a dot plot and box plot?
The box plot shows the median and the dot plot shows the mode.
300
A record store manager asks customers who make a purchase how many hours of music they listen to each day. Is this a biased or unbiased sample? Explain why.
Biased; A person who goes into a record store probably listens to more music than the average person, especially if they spend money to purchase something there.
400
Shelby wants to know what kind of music the majority of 7th grade students listen to. She randomly selects 25 students' names from a hat to survey. Random or not random?
Random
400
Alex goes to Upstate New York to estimate the deer population in a small town there. The first day, he captures and tags 100 deer. The next day, he captures 450 deer and finds that 25 of them have tags. Estimate the population size.
1800 deer
400
One or more samples are favored over another
Biased sample
400
What is the total number of cars sold Monday - Thursday?
14 cars
400
Jack asks the football team which sport is more difficult: basketball or football? Is this a biased or unbiased sample?
Biased; Jack only asked members of the football team and they will likely say that football is more difficult.
500
Gabby wants to know what the height is of the average 7th grade student. She creates a sample using only students who have tall parents. Random or not random?
Not random. Surveys students with tall parents.
500
Miley goes to the rainforest in Brazil to study poisonous dart frogs. The first day she is there, she captures 90 frogs and marks them with paint. The next day, she captures 45 frogs and sees that 40 of them have tags. Estimate the population size.
101.25 frogs
500
Methods for random sample. List 3.
1. Drawling names
2.Cards
3.Dice
4.Technology
5.List
6.Flip a Coin
7. Wheel/Spinner
500
How many candy bars were eaten in total on days 3, 5 and 8?
F
9 candy bars
500
The principal of a middle school wants to know where 8th graders would rather go on their end-of-the-year trip: the city pool or the skating rink. She ONLY surveys the swim team. Is this a biased or unbiased sample?
Biased; She only asked the swim team and they would likely rather go to the city pool.