Sample — Grade 7 Accelerated, what it means and where it is taught
The part of the population you actually measure.
Taught in Grade 7 Accelerated.
Where it is taught
What it rests on
Work through these first if this one does not settle.
- Population — Every member of the group you care about.
Practise this idea
5 questions in the course bank use Sample, in Sampling, Inferences & Comparing Populations.
Problem 1
In a sample of 50 students, 15 prefer pizza. What percent is that?
Worked answer
30
1550 = 0.30
= 30%
Problem 2
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 3
You want to know how much TV the average 7th grader watches. Which sample is biased?
- 60 students drawn at random from the full roster
- Every 5th student leaving the building at dismissal
- Students waiting outside the school television studio
- 60 students picked at random from each grade list
Worked answer
Students waiting outside the school television studio
Students at the TV studio are far more interested in television than a typical student.
That makes them over-represent heavy viewers — a biased sample.
The other three give every student a fair chance of selection.
Problem 4
A factory samples 80 items and finds 24 defective. Estimate the number of defective items in a batch of 1,500.
Worked answer
450
2480 = 0.30
0.30 × 1500 = 450
Problem 5
A biologist tags 60 fish and releases them. Later a sample of 45 fish contains 9 tagged ones. Estimate the lake's fish population.
Worked answer
300
Sample fraction tagged: 945 = 15
So the 60 tagged fish are about 15 of the lake
60 × 5 = 300 fish