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SAT Math skill page

SAT Sampling and Margin of Error Practice

Decide what a sample can represent and use margin of error to describe a reasonable interval around an estimate.

Practice sampling and margin of error in Dolphin SATPractice questions
12-18 min practice time3 questions on pageProblem Solving and Data Analysis
Practice time12-18 min
Question bank3 questions
Best forProblem Solving and Data Analysis

What this tests

What to know for this SAT skill

Dolphin question bank

Practice your skill

Question 1 of 3Easy
In a random sample of 200 students, 62% prefer a later school start. About how many students in a school of 2,000 would be expected to prefer a later start?
  1. 124
  2. 620
  3. 1,000
  4. 1,240
Show answer and solution
Correct answerD. 1,240

Solution walkthrough

  1. Use the sample proportion as an estimate for the population: 0.62 * 2,000 = 1,240.
Question 2 of 3Medium
A survey estimates that 48% of voters support a proposal, with a margin of error of 4 percentage points. Which interval is supported?
  1. 44% to 52%
  2. 46% to 50%
  3. 48% to 52%
  4. 40% to 56%
Show answer and solution
Correct answerA. 44% to 52%

Solution walkthrough

  1. Subtract and add 4 percentage points: 48 - 4 = 44 and 48 + 4 = 52.
Question 3 of 3Hard
Two random surveys use the same method. Survey A samples 100 people, and Survey B samples 1,600 people. Which survey will generally have the smaller margin of error?
  1. Survey A
  2. Survey B
  3. They must be equal
  4. It cannot depend on sample size
Show answer and solution
Correct answerB. Survey B

Solution walkthrough

  1. With the same sampling method, a larger random sample generally produces a smaller margin of error.

Avoid these traps

Common mistakes on this skill

Generalizing from a biased sample

A large sample can still be misleading if the selection method systematically excludes part of the population.

Treating margin of error as a percent multiplier

When margin of error is stated in percentage points, add and subtract it directly from the estimate.

Assuming a sample result is exact

A sample estimates a population value; the margin of error communicates the expected uncertainty.

Study plan

How to practice this skill in Dolphin

  1. Identify the population the study wants to describe.
  2. Check whether the sample was selected in a representative way.
  3. Use the sample proportion to estimate a population value when asked.
  4. Add and subtract the margin of error to form the supported interval.
Practice sampling and margin of error in Dolphin SAT

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FAQ

Questions about SAT Sampling and Margin of Error Practice

What is margin of error on the SAT?

It describes how far a sample estimate may reasonably be from the true population value.

Does a larger sample always remove bias?

No. A larger sample usually reduces random sampling error, but it does not repair a biased selection method.

Can a sample be used to estimate a whole population?

Yes, when the sample is selected randomly and represents the population the study intends to describe.