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7th grade · Math · Unit 16 of 17

Samples & Populations

Random samples and estimates

What your child practices

Telling a sample from a population, choosing a fair random sample, and using sample results to estimate for a whole population.

Maine Learning Results learning standard: 7.SP.A.1; 7.SP.A.2 · using random samples to draw inferences about a population

How we explain it

Children can open this short lesson before they practice.

  1. The population is the whole group. A sample is part of it.
  2. A random sample gives everyone an equal chance to be picked.
  3. Use the sample's fraction to estimate for the population.

Example: In a random sample of 50 students, 10 bike to school. About how many of 400 students bike? 10/50 = 1/5. 1/5 of 400 = 80. Answer: About 80

Samples & Populations in Maine

In the Maine Learning Results, this is unit 16 of 17 in 7th grade Math, after Angle Relationships and before Scale Drawings.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Maine Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    You want to know how voters in a city feel about a new park. Which sample is most likely to represent the population?

    • 200 voters picked at random from the city's voter list
    • 200 people at a park opening
    • the first 200 people who email the city
    • 200 people who live next to the park

  2. Question 2

    In a random sample of 25 students, 9 ride the bus. About how many of the 325 students at the school ride the bus?

    • 208
    • 117
    • 90
    • 142

  3. Question 3

    One random sample has 30 people and another has 300. Which estimate of the population is likely to be closer?

    • The sample of 300
    • The sample of 30
    • They will always be exactly the same

  4. Question 4

    A factory tests 25 light bulbs from a batch of 5000. What is the population?

    • all 5000 light bulbs
    • the boxes of bulbs
    • the 25 bulbs tested
    • the factory workers

  5. Question 5

    You want to know how many hours teens in a town spend online. Which sample is most likely to represent the population?

    • 100 teens at a video game store
    • 100 teens chosen at random from the town's high schools
    • 100 members of the town's running club
    • the 100 teens who answer an online poll

  6. Question 6

    In a random sample of 40 students, 27 have a library card. About how many of the 360 students at the school have a library card?

    • 117
    • 243
    • 270
    • 283

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