Making Inferences on Random Samples

Using Random Sample to Draw Inferences

Open Ended

What is the difference between populations and samples?

Let's Play: Population or Sample

On your whiteboard determine whether the data collected in each survey represent a population or a sample.

Ms. Raymond concludes that 76% of the students in the school have at least one sibling after she conducts a survey of her class.

Let's Play: Population or Sample

On your whiteboard determine whether the data collected in each survey represent a population or a sample.

Paul reports that one out of every five players on the boys’ varsity basketball team can dunk a basketball after he conducts a survey of the players on the team.

Let's Play: Population or Sample

On your whiteboard determine whether the data collected in each survey represent a population or a sample.

After examining 24 loaves of bread at a local grocery store, Nadia concludes that two loaves out of every 24 are multi-grain bread.

What is the difference between a random and a biased sample?

Random or Biased

Ms. Olsen, the Drama Club teacher, writes the names of each of the fifteen team members on separate slips of paper. She puts the slips of paper inside a bag, shakes it, and selects three slips of paper without looking. The three members whose names are selected will complete a survey about the Drama Club.

Vincent chooses each player on his basketball team whose name has five letters to participate in a survey about school sports.

Multiple Choice

Mr. Tamez chooses the first seven students to raise their hands in his math class to participate in a survey.

• Random

• Biased/Not Random

Multiple Choice

Ms. Searcy has 36 students in her English class. The students are seated in 6 rows. The students in each row are assigned a different number 1 through 6. Ms. Searcy rolls a 6-sided number cube to select a row. She rolls it again to select one of the students in that row. The selected student is given a survey about Ms. Searcy’s English class.

• Random

• Biased/Not Random

Multiple Choice

A local coffee shop is conducting a survey to gather information about the coffee consumption of the town’s residents. They hand a survey to the first 50 customers of the day.

• Random

• Biased/Not Random

Multiple Choice

Customers at Bull’s Eye Grocery can win a $25 gift card for throwing a bull’s-eye on the dart board after they check out. Winners are also given a survey about their shopping experience at Bull’s Eye Grocery.

• Random

• Biased/Not Random

Lets try it!

A shipment to a warehouse consists of 3,500 MP3 players. The manager chooses a random sample of 50 MP3 players and finds that 3 are defective. How many MP3 players in the shipment are likely to be defective?

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Fill in the Blank

A band has sold out a concert with 4,200 seats. A random sample of 120 ticket buyers is surveyed, and 28 buyers made their purchase on the first day tickets were being sold. How many of the 4,200 tickets are likely to have been purchased on the first day they were available?

A college conducted a survey of randomly selected freshmen about their choice of major. The table shows the result of the survey.

Which inference about all freshmen at this college is best supported by this information?

F The number of freshmen who chose English as their major is less than

    the number of freshmen who are Undecided on their major.

G The number of freshmen who chose Education as their major is greater 

    than the number of freshmen who chose Science or Other as their major.

H The number of freshmen who chose Business or Education as their major

    is less than the number of freshmen who chose Science or Engineering 

    as their major.

J The number of freshmen who chose Business as their major is greater 

   than the number of freshmen who chose English as their major.

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Making an inference using data from a table!

Multiple Choice

The manager of a music store surveyed a random sample of customers who shop in the store about their favorite type of music. The table shows the number of customers who selected each type of music.

Based on the information in the table, which inference about the favorite type of music of all the customers who shop in the music store appears to be valid?

• they are certain to select rock or pop music.

• They are less likely to select country or rap music than rock music.

• They are more likely to select country music than jazz, classical, or rap music.

• They are certain to select any type of music other than jazz music.