Formulating Hypotheses

Research in psychology begins with a question or an observation about human behaviour. Before conducting any study, psychologists must formulate clear, testable statements about what they expect to find. These statements are called hypotheses.

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What is a Hypothesis?

A hypothesis is a clear, testable, predictive statement about the expected outcome of a study. It is not a question — it is a statement that can be tested through research and either supported or refuted by the evidence.

Characteristics of a Good Hypothesis

• Testable — it must be possible to design a study to test it
• Specific — it must clearly state what is being measured and what the expected outcome is
• Operationalised — the variables must be defined in measurable terms

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Types of Hypothesis

1. Alternative Hypothesis (Experimental Hypothesis)

The alternative hypothesis (H₁ or Hₐ) states that there will be a difference, relationship, or effect. This is what the researcher expects to find.

There are two forms:

Directional (one-tailed) hypothesis — predicts the direction of the difference or relationship:

• Example: "Participants who revise using spaced practice will score higher on a memory test than participants who use massed practice"

Non-directional (two-tailed) hypothesis — predicts that there will be a difference but does not specify the direction:

• Example: "There will be a difference in memory test scores between participants who use spaced practice and those who use massed practice"

2. Null Hypothesis

The null hypothesis (H₀) states that there will be no difference, relationship, or effect — any observed difference is due to chance.

• Example: "There will be no significant difference in memory test scores between participants who use spaced practice and those who use massed practice. Any difference is due to chance."

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When to Use Directional vs Non-Directional Hypotheses

Type	When to Use	Example
Directional	When previous research or theory suggests a clear direction for the result	"Students with growth mindset will score higher..."
Non-directional	When the area is under-researched or previous findings are contradictory	"There will be a difference in scores..."

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Operationalisation of Variables

Operationalisation means defining variables in a way that can be measured and tested. Vague terms must be made specific.

Vague Term	Operationalised Version
"Memory"	Score on a 20-word recall test
"Anxiety"	Score on a standardised anxiety questionnaire (e.g. State-Trait Anxiety Inventory)
"Intelligence"	Score on a standardised IQ test
"Aggression"	Number of aggressive acts observed in a 10-minute period

Exam Tip: Always operationalise variables in your hypotheses. Instead of "Stress affects memory," write "Participants who complete a stressful task (giving a speech to strangers) will recall fewer words from a 20-word list than participants who complete a non-stressful task (reading quietly)."

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Aims vs Hypotheses

An aim is a general statement of what the study intends to investigate. A hypothesis is a specific, testable prediction.

Feature	Aim	Hypothesis
Specificity	General	Specific and testable
Example	"To investigate whether sleep affects memory"	"Participants who sleep for 8 hours will recall more words from a 20-word list than participants who sleep for 4 hours"

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Key Points

• A hypothesis is a clear, testable, predictive statement.
• Alternative hypothesis: predicts a difference or effect (directional or non-directional).
• Null hypothesis: predicts no difference — any result is due to chance.
• Variables must be operationalised — defined in measurable terms.
• Aims are general; hypotheses are specific and testable.