Prediction From Sampling

If I wanted to know how many blades of grass are inside the track, which sampling method could I use?

• Have my students count every blade of grass

• Guess

• Divide the grassy area into 1 inch sections, randomly pick several sections to count, average them together and multiply that by the total square inches.

True or False: all samples lead to a good prediction about an entire population.

• True

• False

The table shows the results of a survey of 200 people attending a hockey game.
The attendance for the hockey game is about 25,000 visitors each game.  Based on the table, how many people out of 25,000 could be expected to buy a pennant?

• 1,375

• 1,650

• 2,750

• 3,850

A high school has 1500 students.  In a random sample of 50 students, 32 own one or more pets.  Predict the number of students at the high school who own one or more pets.

• 480

• 960

• 48

• 96

A random sample of 80 books at a library showed that 32 books were fiction. Predict the total number of fiction books in a library that has 400 books.

• 160

• 200

• 140

• 120

Answer explanation

To find the total number of fiction books in the library, we can set up a proportion: 32 books out of 80 are fiction, so 400 books would have (32/80) * 400 = 160 fiction books.

Tags

CCSS.7.RP.A.3

A random sample of 50 students from a school shows that 28 students prefer online classes over traditional classes. Predict how many students out of 200 would prefer online classes.

• 112

• 56

• 140

• 100

Answer explanation

Since 28 out of 50 students prefer online classes, the proportion is 28/50. Extrapolating to 200 students gives 112 students who would prefer online classes.

Tags

CCSS.7.RP.A.3

In a random sample of 30 cookies, 9 cookies have chocolate chips. Predict how many cookies will have chocolate chips if 150 cookies are made.

• 45

• 30

• 60

• 75

Answer explanation

Since 9 out of 30 cookies have chocolate chips, the proportion is 9/30. Applying this proportion to 150 cookies gives 45 cookies with chocolate chips.

Tags

CCSS.7.RP.A.3

A study on a random sample of 250 cars passing through a toll booth shows that 75 cars are from out of state. Predict the number of out-of-state cars among 1000 cars passing through the toll booth.

• 300

• 250

• 200

• 350

Answer explanation

To predict the number of out-of-state cars among 1000 cars, use the ratio from the sample: 75/250 = x/1000. Solving for x gives 300.

In a random sample of 60 apples from a farm, 12 apples were found to be rotten. If the farm has 3000 apples, predict the number of rotten apples.

• 600

• 240

• 120

• 480

Answer explanation

To predict the number of rotten apples, use the ratio of rotten apples in the sample to the total apples in the farm: (12/60) * 3000 = 240 rotten apples.

Tags

CCSS.7.RP.A.3

A random sample of 200 people at a concert shows that 120 people are wearing hats. Predict the number of people wearing hats if 800 people are at the concert.

• 480

• 320

• 600

• 400

Answer explanation

To predict the number of people wearing hats for 800 attendees, use the ratio of people wearing hats in the sample. 120/200 = x/800. Solving for x gives 480.

Tags

CCSS.7.RP.A.3