Give one strength and one weakness of random sampling.

Random sampling avoids researcher bias because the researcher does not choose who takes part. A random sample may still be unrepresentative by chance, and a full list of the population is needed.

What is stratified sampling?

Stratified sampling divides the target population into subgroups, such as age groups. Participants are then picked randomly from each subgroup in proportion to its size in the population.

A school has 800 students: 480 girls and 320 boys. How many of each should a stratified sample of 40 contain?

The sample should contain 24 girls and 16 boys. Girls make up 480 ÷ 800 = 60% of the school, and 60% of 40 is 24.

Edexcel GCSE Psychology 1PS0

Development

Topic overview Early brain development Piaget's theory of cognitive development Dweck's mindset theory and Willingham's learning theory The three mountains task and Gunderson's praise study The development of morality

Memory

Topic overview Information processing, duration and capacity Retrograde and anterograde amnesia Bartlett's theory of reconstructive memory The multi-store model, reductionism and holism War of the Ghosts and the Peterson and Peterson study

Psychological Problems

Topic overview Symptoms of depression and addiction Incidence and effects of mental health problems Explaining depression Explaining addiction Treating depression and addiction Key studies and the nature–nurture debate

The Brain and Neuropsychology

Topic overview Lobes of the brain and the effects of damage Lateralisation and Sperry's split-brain study Neurons, synapses and the central nervous system Phineas Gage and how brain research has changed

Social Influence

Topic overview Conformity to majority influence Obedience to authority Bystander intervention Crowd behaviour, society and culture Piliavin's subway study and the Stanford prison study

Criminal PsychologyOptional topic

Topic overview Operant conditioning and social learning explanations of crime Eysenck's criminal personality theory Punishment, recidivism and rehabilitation Bandura's Bobo doll study and Charlton's St Helena study

The SelfOptional topic

Topic overview Self-concept and influences on self-esteem Erikson's identity stages and belief in free will Rogers' and Maslow's humanistic theory Measuring personality and trait theory Vohs and Schooler's cheating study and Van Houtte and Jarvis's pet study

PerceptionOptional topic

Topic overview Depth cues, visual illusions and constancies Gibson's direct theory and Gregory's constructivist theory Perceptual set The Haber and Levin and Carmichael studies

Sleep and DreamingOptional topic

Topic overview Sleep stages and the sleep cycle Influences on sleep and sleep disorders Freud's theory of dreaming and activation synthesis theory Freud's Little Hans and Siffre's cave study

Language, Thought and CommunicationOptional topic

Topic overview Piaget and Vygotsky on language and thought Linguistic relativism and determinism Human and animal communication Non-verbal communication and Darwin's evolutionary theory The Yuki and Boroditsky studies

Research Methods

Topic overview Variables, hypotheses and controls Sampling methods Experiments and experimental designs Interviews, questionnaires and types of data Correlations, case studies and observations Ethical issues in psychological research Evaluating studies and the core areas of psychology Averages, calculations and graphs

Research Methods

Sampling methods

3 things to know
Papers 1 and 2

Overview

Target populations, random, stratified, volunteer and opportunity sampling with their strengths and weaknesses, stratified sample calculations, and sampling bias.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a target population?

Key term

Why do researchers usually study a sample rather than the whole target population?

Key term

How is a random sample selected?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a target population?
Model answer
A target population is the whole group of people a researcher wants the findings to apply to. A sample is selected from the target population.
2
Why do researchers usually study a sample rather than the whole target population?
Model answer
A target population is usually too large for everyone to be tested. A representative sample allows the findings to be generalised to the whole group.
3
How is a random sample selected?
Model answer
Every member of the target population has an equal chance of being chosen. Names can be drawn from a hat or picked by a computer.
4
Give one strength and one weakness of random sampling.
Model answer
Random sampling avoids researcher bias because the researcher does not choose who takes part. A random sample may still be unrepresentative by chance, and a full list of the population is needed.
5
What is stratified sampling?
Model answer
Stratified sampling divides the target population into subgroups, such as age groups. Participants are then picked randomly from each subgroup in proportion to its size in the population.
6
A school has 800 students: 480 girls and 320 boys. How many of each should a stratified sample of 40 contain?
Model answer
The sample should contain 24 girls and 16 boys. Girls make up 480 ÷ 800 = 60% of the school, and 60% of 40 is 24.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Development

Memory

Psychological Problems

The Brain and Neuropsychology

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Long-term memory can last for a .

lifetimeminutesecond

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe median is 10.

BIn order the scores are 4, 7, 9, 11, 15 and 18.

CThe middle two scores give (9 + 11) ÷ 2 = 10.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Short-term memory can hold about 7 ± 2 items at once.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Research Methods, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.