← ACARA Digital Technologies Years 9–10

Population and sample

The part of a population you collect data from. It must represent the whole population, so use a big enough size, choose randomly and avoid sampling bias.

Part of: ACARA Digital Technologies Years 9–10 — Acquiring and Validating Data — Module 20

Understanding Population and sample in ACARA Digital Technologies Years 9–10

What it does: Choosing only the people close by, like friends in your class, is a convenience sample and can lead to sampling bias. random.sample() picks 40 students from all_students by chance, so each student has an equal chance, which is how a random sample works. Very small samples can be thrown off by a few unusual people. A bigger sample usually gives more reliable results. A convenience sample uses whoever is easiest to reach. It is quick but often does not represent the population. A good sample includes a mix of the people in the population. The committee members are a biased group, and Year 10 alone leaves out the other year levels.

Common mistakes: A sample is only part of a population. A sample of 150 cannot be taken from a population of 100. The sample size must be smaller than 100, for example 30. pop[:40] takes the first 40 students, which is a convenience sample and not random. It should use random.sample(pop, 40) so every student has an equal chance of being chosen.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Population and sample to a class →

This module's key terms are also in a printable crossword (Modules 226–254) and word search (Modules 226–329).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

A school has 1,200 students. You survey 60 of them about canteen food. What is the 60 students?

The populationThe sample

Matches

population = 1200 sample = 1200 # survey a sample of the whole school

↓

The sample is the same as the population, so this is a census, not a sample. A sample is only a part of the population, such as 100 students.

Applying

Meanings

Term

sample

Meaning

The part of a population you collect data from. It must represent the whole population, so use a big enough size, choose randomly and avoid sampling bias.

Practice

population ← all 900 students in the school

Testing

Gaps

=(1,500)

Check Answer

Spots

1pop = list(range(1, 101))

2s = random.sample(pop, 150)

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy

Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games

Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print

Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. A school has 1,200 students. You survey 60 of them about canteen food. What is the 60 students?

A. The sample ✓

B. The population

The sample is the part you collect data from. The population is the whole group, here all 1,200 students.

2. Which statement about sample size is better?

A. A sample of 3 people is always enough for any population

B. A larger sample usually represents the population more reliably ✓

Very small samples can be thrown off by a few unusual people. A bigger sample usually gives more reliable results.

3. Which is a random sample of your year level?

A. Asking the 50 friends sitting near you at lunch

B. Drawing 50 student ID numbers at random from the full class list ✓

In a random sample every member of the population has an equal chance of being picked. Asking friends is a convenience sample.

4. Which is a convenience sample?

A. Surveying only the students who are standing near the library ✓

B. Using a random number generator to pick students from the roll

A convenience sample uses whoever is easiest to reach. It is quick but often does not represent the population.

5. You want to know how all students travel to school, but you survey only students at the bus stop. What is the problem?

A. Sampling bias: bus users are over-represented ✓

B. No problem: any group of students will give the same answer

Sampling bias happens when some members of the population are more likely to be included than others. This sample leaves out walkers, cyclists and students who are driven.

Match the Pairs

sample_size = 150 → Sets how many members of the population are included in the sample. A bigger sample usually represents the population better.

sample = random.sample(population, 50) → Picks 50 members of the population completely by chance, so each member has an equal chance of being chosen (a random sample).

A convenience sample only uses the people who are easiest to reach, so it may not represent the whole population. → sample = friends_in_my_class

A random sample gives every member of the population an equal chance of being picked. → sample = random.sample(all_students, 40)

population = 1200 sample = 1200 # survey a sample of the whole school → The sample is the same as the population, so this is a census, not a sample. A sample is only a part of the population, such as 100 students.

sample = 5 # 5 students represent a school of 1200 → The sample size is too small to represent a population of 1200, so the results could be unreliable. A larger sample is needed.

Key Term

sample

The part of a population you collect data from. It must represent the whole population, so use a big enough size, choose randomly and avoid sampling bias.

Fill in the Blanks

1. =RANDBETWEEN(1,500)

Hint: Type the function that picks a random whole number between two limits, so each student ID from 1 to 500 has an equal chance.

2. =COUNTA(A2:A501)

Hint: Type the function that counts non-empty cells to find the population size from a list of names.

3. SELECT * FROM students ORDER BY RANDOM() LIMIT 5;

Hint: Type the SQL function that shuffles the rows into a random order, so the 5 students chosen are a random sample.

4. =COUNTA(D2:D31)/COUNTA(A2:A501)

Hint: Type the arithmetic operator that divides the sample size by the population size to give the fraction sampled.

5. =IF(COUNTA(A2:A31)<30,"Too small","OK")

Hint: Type the function that tests whether the sample size is big enough and then shows one of two messages.

Spot the Error

Question 1

A pop = list(range(1, 101))

B s = random.sample(pop, 150)

C print(len(s))

Line B — A sample is only part of a population. A sample of 150 cannot be taken from a population of 100. The sample size must be smaller than 100, for example 30.

Question 2

A pop = all_students

B s = pop[:40]

C print(len(s))

Line B — pop[:40] takes the first 40 students, which is a convenience sample and not random. It should use random.sample(pop, 40) so every student has an equal chance of being chosen.

Question 3

A population = 100

B sample = 120

C print(sample / population)

Line A — The population is the whole group, so it must be larger than the sample. A population of 100 is smaller than the sample of 120. It should be population = 1200.

Question 4

A def pick(p, n):

B return random.sample(p, n)

C s = pick(50, students)

D print(len(s))

Line C — The arguments are in the wrong order. pick() expects the population first and then the sample size, so the call should be pick(students, 50).

Question 5

A pop = load_students()

B n = 80

C s = random.sample(pop, n)

D print('Sample:', len(pop))

Line D — len(pop) gives the size of the whole population, not the sample. The sample size is len(s), so the line should be print('Sample size:', len(s)).

Student with a class code? Join your class →