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A Level · Cambridge (CIE) · 9990

Write and apply research hypotheses

Turn a research question into a testable null hypothesis or a directional or non-directional alternative with clear variables.

Section Paper 4 · Specialist Options: Application and Research Methods

Cambridge International AS & A Level Psychology 9990 · 2028–2030 · Version 1 · AL-HYPOTHESES
Exam scope and assessment notes

Original StudyForA teaching mapped to the Cambridge 2028–2030 syllabus. These lessons are independent study support, not Cambridge material, official mark schemes or awarded grades. No lesson reproduces a research article or Cambridge question. Human subject-expert review and full timed-paper grading remain pending. This is one of the five additional A Level methodology areas and supports Paper 4 planning; it does not replace teaching the selected specialist options or a timed Paper 4 practice set.

Before you begin

  • This lesson supports the 2028–2030 Version 1 A Level Psychology route. Review the AS research-method foundations first, then apply the method to the specialist options your school selects.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

A hypothesis predicts that notification exposure and recall will be related, without saying in which direction. What type is it?

What you will learn

  • Write a null hypothesis about no predicted difference or relationship
  • Write one-tailed directional and two-tailed non-directional alternatives
  • Match a hypothesis to the method, population and operationalised variables

Begin with an aim and measurable variables

An aim states what a study investigates. Before writing a hypothesis, define who is studied, which conditions or co-variables are compared, and how the outcome is measured.

A hypothesis predicts a pattern that can be checked against data. Operational definitions make it clear what counts as each condition and outcome; broad claims such as 'attention will improve' need a specified task and scoring rule.

Null and alternative hypotheses make different predictions

A null hypothesis predicts no difference between specified conditions or no relationship between specified co-variables in the population. Avoid claiming that a study proves a universal absence of an effect.

An alternative hypothesis predicts a difference or relationship. A directional, one-tailed hypothesis states which group is expected to score higher or whether the relationship is positive or negative. A non-directional, two-tailed hypothesis predicts a difference or relationship without selecting its direction.

Choose direction before examining the outcome

Use a directional prediction only when theory or prior evidence justifies a specific direction before the data are observed. Otherwise, a non-directional prediction avoids choosing a direction after seeing which result occurred.

Match the wording to the design. An experiment may predict a difference between conditions; a correlational study predicts a relationship between co-variables and cannot, by itself, show that one causes the other. A clear hypothesis does not guarantee that the prediction will be supported.

Sources for this lesson

Pause and explain

Which statement is suitable for a correlational study of practice time and test score?

Put the idea to work

Worked example

A researcher compares recall after quiet study and study with notifications. Write one non-directional alternative and its null hypothesis.

Show the worked solution
  1. Define the two revision conditions and a recall measure.
  2. The alternative must say 'a difference' without predicting which condition scores higher.
  3. The null must predict no difference in the measured outcome.

Answer Alternative: There will be a difference in the number of words correctly recalled after quiet study and after study with notifications. Null: There will be no difference in the number of words correctly recalled after the two study conditions.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

Test this topic →

From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

A researcher measures the number of words recalled after quiet revision or revision with phone notifications. Write a directional alternative hypothesis predicting fewer recalled words with notifications.

Give me a hint

Name both conditions and the measurable score.

Compare my reasoning
  1. Specify the participants or sample being studied.
  2. Define the outcome as the number of list words recalled correctly after the same interval.
  3. State the predicted direction between notification and quiet conditions.

Among the sampled learners, those revising with phone notifications will recall fewer list words correctly after the fixed interval than those revising in quiet.

Look for these in your work

  • Conditions compared
  • Recall outcome is operationalised
  • Direction is explicit
2 · Independent

A study finds a positive correlation between weekly sleep duration and recall score. Write a suitable non-directional alternative and explain one limit.

Give me a hint

Use the term 'relationship'; do not describe an assigned condition.

Compare my reasoning
  1. Name both co-variables: weekly sleep duration and recall score.
  2. Predict that a relationship exists without selecting its direction.
  3. State that correlation alone cannot show whether sleep caused score differences or another factor affected both.

There will be a relationship between weekly sleep duration and recall score among the sampled learners. The correlation cannot establish that sleep duration caused the scores; factors such as health or workload may relate to both.

Look for these in your work

  • Both co-variables named
  • Non-directional prediction used
  • Causal limit stated
3 · Transfer

A school wants to know whether a new optional retrieval-practice routine changes the number of correct answers on a short quiz. Write a null and one justified alternative.

Give me a hint

Define the compared conditions and the same quiz outcome first.

Compare my reasoning
  1. Compare routine users with a clearly defined usual-practice group, or specify a repeated-measures plan.
  2. Define outcome as number of correct answers on the same quiz under the same time limit.
  3. State no difference for the null; choose a directional alternative only if prior evidence supports a direction, otherwise make it non-directional.

Null: There will be no difference in the number of correct answers between learners assigned to the retrieval-practice routine and learners using usual practice. A non-directional alternative is that there will be a difference. Use a one-tailed alternative only when a justified prediction is set in advance.

Look for these in your work

  • Conditions and outcome defined
  • Null predicts no difference
  • Alternative direction is justified or left open

Common mistakes

  • Writing an aim as if it were a hypothesis
  • Leaving the population or measure too vague to test
  • Calling a correlational relationship a causal effect
  • Choosing a directional hypothesis after inspecting the results
  • Using 'no effect' without specifying the conditions and outcome
Recall without your notes

What can you explain now?

What extra prediction does a directional alternative make?

Compare with the explanation

It states the expected direction of a difference or relationship, not merely that one exists.

The direction should be justified before the researcher sees the outcome data.

After trying it yourself, choose your next review. This is your self-assessment.

Your review choice appears on Today. Sign in to sync it across devices.

Make it stick

How do null, directional alternative and non-directional alternative hypotheses differ, and why must a hypothesis fit the research design?

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Psychology

Course scope and assessment

Seven original lessons map all 15 AS research-method and methodological-concept sections to explained Guided, Independent and Transfer practice. All 12 compulsory AS core studies have original study-specific teaching and staged practice; five additional A Level methodology lessons cover research design and validity. All 15 Clinical, all 15 Consumer (2.1.1–2.5.3) and all 15 Health (3.1.1–3.5.3) Psychology sections link to original teaching and staged practice. All 15 Organisational Psychology sections 4.1–4.5 now have original teaching and explained staged practice; the six new 4.4–4.5 lessons bring the planning map to 92 of 92 indexed sections. Consumer lessons cover physical and psychological environments; decision models, heuristics and mistakes; packaging, selling and buying; advertising, self-monitoring, product placement, brand recognition and slogans. Evaluation boundaries are explicit: studies use particular products, samples, tasks and settings; gaze, recall, self-report, EEG indices, ratings, choices and purchases are different outcomes. Health evidence is bounded: Laba et al. measured hypothetical preferences; Riekert and Drotar raise a non-response concern; Chung and Naya's cap tracked openings, not swallowing; Chaney et al. was a short caregiver-reported pilot; Yokley and Glenwick examined immunisation attendance in one public-health setting. MacLachlan et al. report one patient, not a controlled treatment effect; Brudvik et al. compared separate child, parent and physician ratings in one emergency department. Chandola et al. found a cohort association; Wang et al. measured responses during a monitored arithmetic task; Evans and Wener observed commuters; Bridge et al. found mixed self-rated outcomes in radiotherapy. Janis and Feshbach measured short-term self-reports in one school; Lewin et al. tested a rehabilitation package, not information alone. Tapper et al. and Fox et al. studied bounded school and worksite programmes; incentive effects do not establish transfer or rule out reporting effects. Weinstein measured comparative expectations, while Seligman’s framework is conceptual and Shoshani and Steinmetz used a school-level comparison. These findings do not establish universal health effects or diagnose individuals. Need-theory examples use a child measurement study, not a workplace test; SMART is a practical checklist, not a motivational theory. Landry et al. compared reward framing with student volunteers in a lab; this does not establish universal effects in workplaces. Cuadrado et al. (2008) measured undergraduate evaluations of presented leaders, not workplace performance or hiring; this does not establish a universal gender effect. The historical 1995 Munchausen criteria are not a current diagnostic checklist. Cambridge’s 2028–2030 Reference List treats Oruč et al. (1997) as an example of genetic explanation although its participants had bipolar I; gambling disorder is listed in Cambridge’s Clinical topic but classified under addictive behaviours in ICD-11. Candidates choose two options, but all four remain listed so schools can select a route. The 92-section count is a planning index, not a Cambridge score. Remaining work is deeper coverage review, separate-year syllabus reconciliation, timed-paper practice and human subject-expert review. The separate 2027 and 2024–2026 syllabuses are not reconciled into this route. Practice is not official grading, a timed-paper simulation or human subject-expert review.

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