Random sample — Grade 7 Accelerated, what it means and where it is taught
Every member has an equal chance of being picked — the only kind you can trust.
Taught in Grade 7 Accelerated.
Where it is taught
Practise this idea
3 questions in the course bank use Random sample, in Sampling, Inferences & Comparing Populations, Sampling, Simulation & Inference.
Problem 1
In a random sample of 200 voters, 84 support a measure. Estimate how many of 5,000 voters support it.
Worked answer
2100
84200 = 0.42
0.42 × 5000 = 2100
About 2,100 voters.
Problem 2
Why is a random sample preferred?
- It has no systematic tilt
- It is always larger
- It is cheaper
- It avoids the need for a margin of error
Worked answer
It has no systematic tilt
Random selection gives every member an equal chance
So errors are noise, not bias
Problem 3
Estimate the margin of error for a random sample of 400, as a percent.
Worked answer
5
1√400=120=0.05