2023 May/June · Paper 22 · Q12 marksControls and standardisation
2023 May/June · Paper 22 · Q66 marksControls and standardisation
2023 May/June · Paper 22 · Q7 (a(iii))1 markExperimental designs
2022
2022 Oct/Nov · Paper 22 · Q9 (a, b)4 marksControls and standardisation · Experimental designs
2022 May/June · Paper 22 · Q9 (d)3 marksExperimental designs
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References only, not question text. Open Official paper ↗ where Cambridge publishes the paper,
or see the official Cambridge past-papers page; for other papers, ask your
school. “Paper 42” means Paper 4, variant 2.
Practice questions
Original questions written by HomiLabs in the style of the exam, with answers and mark schemes. They are not
Cambridge past paper questions and have not been reviewed by Cambridge. Try each one before opening the answer.
Q1Experimental designs · Core · Paper 2 style · 3 marks
(a)Outline what is meant by an independent measures design.[1]
(b)A hypothetical experiment in Quetta compares memory for pictures and memory for words using an independent measures design. Explain one weakness of this design for this study.[2]
Show answer
(a) Different participants take part in each condition of the experiment.
1 mark.
(b) Participant variables such as natural memory ability may differ between the picture group and the word group, so differences in recall may be due to the people rather than the type of material.
1 mark weakness; 1 mark linked to context.
Q2Experimental designs · Core · Paper 2 style · 4 marks
(a)Explain what is meant by an 'order effect' in a repeated measures design.[2]
(b)Describe how counterbalancing could be used in a repeated measures experiment on whether people type faster on a laptop keyboard or a phone screen.[2]
Show answer
(a) A change in performance caused by the order in which the conditions are done rather than by the IV, e.g. doing better in the second condition through practice, or worse through fatigue or boredom.
1 mark definition; 1 mark example (practice / fatigue / boredom).
(b) Split participants into two halves: one half types on the laptop first and then the phone; the other half uses the phone first and then the laptop, so order effects are balanced across the conditions.
1 mark: two groups in opposite orders; 1 mark: in context.
Q3Experimental designs · Core · Paper 2 style · 4 marks
(a)Describe how a researcher could use a matched pairs design in a hypothetical experiment comparing two diets for weight loss among adults in Lagos.[3]
(b)Give one disadvantage of using a matched pairs design in this study.[1]
Show answer
(a) Measure each volunteer's starting weight (and perhaps age and sex); pair people with similar starting weight; randomly allocate one member of each pair to diet A and the other to diet B.
1 mark: pre-measure a relevant variable; 1 mark: form pairs; 1 mark: one of each pair to each condition (randomly).
(b) It is time-consuming to measure and match people, and if one member of a pair drops out the other's data may be lost (or matching cannot be perfect on all variables).
1 mark.
Q4Experimental designs · Core · Paper 2 style · 3 marks
A hypothetical experiment with 48 participants in Hong Kong tests whether people compare shop prices faster when the prices are shown as a vertical bar chart or as a horizontal bar chart. Each participant does both conditions; half do vertical first and half do horizontal first.
(a)How many participants should do the order 'vertical chart first, then horizontal chart'?[1]
(b)Name the technique the researcher is using and state its purpose.[2]
Show answer
(a) 24
48 ÷ 2 = 24.
(b) Counterbalancing (ABBA / two orders); to balance out order effects such as practice and fatigue between the two conditions.
1 mark name; 1 mark purpose.
Q5Experimental designs · Core · Paper 2 style · 2 marks
(a)A hypothetical study compares the spatial ability of left-handed and right-handed people. Explain why it must use an independent measures design.[2]
Show answer
(a) Handedness is a characteristic of the participant that cannot be changed, so each person can only be in one condition (left-handed or right-handed).
1 mark: IV is a participant characteristic / not manipulated; 1 mark: so cannot be in both conditions.
Q6Experimental designs · Core · Paper 2 style · 3 marks
(a)Describe how a researcher could randomly allocate 30 participants to two conditions.[2]
(b)Explain why random allocation is used.[1]
Show answer
(a) Give each participant a number from 1 to 30, put the numbers in a hat and draw them out; the first 15 drawn go to condition A and the remaining 15 to condition B (or use a random number generator).
1 mark random method; 1 mark equal groups / how it is used.
(b) So that each participant has an equal chance of being in either condition, spreading participant variables evenly and avoiding researcher bias in choosing groups.
1 mark.
Q7Experimental designs · Standard · Paper 2 style · 6 marks
(a)Describe repeated measures design and matched pairs design, using any examples.[6]
Show answer
(a) Repeated measures: the same participants do every condition, e.g. each person takes a memory test in silence and with music. It removes participant variables between conditions and needs fewer participants, but suffers from order effects (practice, fatigue) and demand characteristics, controlled by counterbalancing. Matched pairs: different participants in each condition but each participant is paired with another who is similar on a key variable (e.g. IQ or age), one of each pair going into each condition. It reduces participant variables without order effects, but matching is time-consuming and never perfect.
Up to 3 marks each: description (1), example (1), strength/weakness or control (1).
Q8Experimental designs · Standard · Paper 2 style · 4 marks
(a)A hypothetical study in Islamabad investigates whether students learn new Urdu poetry better when they study it at 8 am or at 8 pm. Explain which experimental design you would choose and why.[3]
(b)Suggest how the researcher could use a repeated measures design instead.[1]
Show answer
(a) Matched pairs (or independent measures): the same poem cannot be learned twice by the same person, so repeated measures would cause practice effects; matching on a pre-test of memory ability reduces participant variables between the 8 am and 8 pm groups.
1 mark design; 1 mark reason against repeated measures (practice/learning the same material); 1 mark reason for chosen design.
(b) Use two different but equally difficult poems (one for each time) and counterbalance which poem is learned at which time.
1 mark.
Q9Experimental designs · Standard · Paper 2 style · 4 marks
A hypothetical experiment tests whether visitors find their way through a large hospital in Kuala Lumpur faster using a printed map or a phone map. The measure is the time taken to walk from the entrance to the eye clinic.
(a)Explain why the researcher should not use a repeated measures design.[2]
(b)Suggest which design should be used and give one strength of it for this study.[2]
Show answer
(a) After the first condition participants would already know the route, so their time in the second condition would be quicker because of learning (a practice effect), not because of the type of map.
1 mark practice/learning effect; 1 mark linked to route.
(b) Independent measures: each participant uses only one map, so there are no order effects and they cannot work out the aim by comparing conditions.
1 mark design; 1 mark strength.
Q10Experimental designs · Standard · Paper 2 style · 4 marks
In a hypothetical driving-simulator study in Sydney, each participant drives for one hour while talking on a hands-free phone and then for one hour while using a hand-held phone. Reaction time to hazards is measured.
(a)Explain how a fatigue effect could affect the results of this study.[2]
(b)Suggest two ways of reducing this problem.[2]
Show answer
(a) In the second hour participants will be tired and bored, so their reaction times will be slower whatever the condition; since the hand-held phone condition always comes second, it will appear worse than it really is.
1 mark tiredness slows reactions; 1 mark confounds the second condition.
(b) Counterbalance the order (half do hands-free first); give a rest break between conditions / shorten each session.
1 mark each.
Q11Experimental designs · Standard · Paper 2 style · 6 marks
A hypothetical experiment in an office training centre in Lahore compares a new keyboard layout with a standard layout. Twelve learners took a typing pre-test and were formed into 6 matched pairs; one member of each pair was randomly allocated to each layout. After two weeks of practice, their typing speeds (words per minute) were:Pair 1: new 42, standard 38Pair 2: new 35, standard 36Pair 3: new 50, standard 44Pair 4: new 28, standard 25Pair 5: new 46, standard 41Pair 6: new 31, standard 30
(a)Calculate the mean typing speed for each layout. Give your answers to 1 decimal place.[2]
(b)State in how many of the pairs the learner using the new layout was faster.[1]
(c)Explain why a matched pairs design was used here rather than a repeated measures design.[2]
(d)Explain one problem that would arise if the learner using the new layout in pair 4 left the study before the final test.[1]
Show answer
(a) New layout: 38.7 words per minute; standard layout: 35.7 words per minute.
(c) With repeated measures each learner would practise on both layouts, so skill learned on the first layout would carry over to the second (an order/practice effect, and the layouts could interfere with each other); matched pairs avoids this while still controlling typing ability, because the pairs were matched on the pre-test.
1 mark: order/practice or interference effect with repeated measures, in context; 1 mark: matching on the pre-test still controls the main participant variable.
(d) The other member of pair 4 has no partner to be compared with, so their data are also lost (or must be excluded), reducing the sample to 5 pairs.
1 mark: partner's data cannot be used / sample reduced.
Q12Experimental designs · Standard · Paper 2 style · 5 marks
In a hypothetical independent measures experiment in Doha, 60 adults were randomly allocated to an 8-week group exercise programme or an individual exercise programme (30 in each). Six people dropped out of the group programme and one dropped out of the individual programme.
(a)Calculate the percentage of participants who dropped out of each condition.[2]
(b)Calculate the percentage of all participants who completed the study. Give your answer to 1 decimal place.[1]
(c)Explain how the uneven drop-out could affect the validity of comparing the two groups.[2]
Show answer
(a) Group exercise: 20%; individual exercise: 3.3% (to 1 d.p.)
6 ÷ 30 × 100 = 20% (1); 1 ÷ 30 × 100 = 3.3% (1).
(b) 88.3%
(60 − 7) ÷ 60 × 100 = 88.3%.
(c) The people who stayed in the group-exercise condition may be the most motivated, so the groups are no longer equivalent; any difference in fitness may be due to motivation (a participant variable) rather than the type of exercise.
1 mark groups no longer equal; 1 mark participant variable confounds result.
Q13Experimental designs · Challenge · Paper 2 style · 5 marks
A hypothetical repeated measures experiment with 36 students in Riyadh tests concentration in three conditions: silence, instrumental music, and speech playing in the background.
(a)Calculate the number of different orders in which the three conditions could be presented.[1]
(b)If each order is used equally, how many participants complete each order?[1]
(c)How many participants do the 'speech' condition first?[1]
(d)Explain why full counterbalancing of all orders is better than just using a single order for everyone.[2]
Show answer
(a) 6
3 × 2 × 1 = 6.
(b) 6
36 ÷ 6 = 6.
(c) 12
2 of the 6 orders start with speech: 2 × 6 = 12 (or 36 ÷ 3).
(d) With one order, the last condition would always benefit from practice or suffer from fatigue, confounding the results; using every order equally means each condition appears in each position equally often, so order effects cancel out.
1 mark problem with single order; 1 mark how full counterbalancing solves it.
Q14Experimental designs · Challenge · Paper 2 style · 4 marks
A hypothetical experiment in schools in Karachi tests whether children aged 8–10 choose a healthy snack more often after watching a cartoon advert for fruit than after watching a cartoon advert for toys.
(a)Explain one strength and one weakness of using an independent measures design rather than a repeated measures design in this study.[4]
Show answer
(a) Strength: each child sees only one advert, so they cannot compare the adverts and guess the aim (fewer demand characteristics) and there are no order effects such as boredom. Weakness: the two groups may differ in participant variables, e.g. some children may already like sweet snacks more, which could explain any difference in snack choice instead of the advert.
2 marks each: point + context (children, adverts, snack choice).
Q15Experimental designs · Challenge · Paper 2 style · 14 marks
(a)Plan a laboratory experiment to investigate whether chewing gum improves short-term memory, using a matched pairs design. Your plan should include details of the variables, the matching procedure, controls and how the data will be analysed.[10]
(b)Explain one weakness of your plan and suggest how it could be improved.[4]
Show answer
(a) Example plan: IV – chewing sugar-free mint gum vs not chewing; DV – number of digits recalled in the correct order on a digit-span test (strings of increasing length, read out by recording). Sample: 40 university students; pre-test on a digit-span test, rank by score, pair adjacent participants, randomly allocate one of each pair to each condition. Controls: same room, same time of day, same recorded instructions and digit lists, gum given 2 minutes before the test, no other food or drink. Ethics: informed consent, right to withdraw, check for allergies, debrief. Data: compare mean (or median) digit span of the two conditions; bar chart.
Level 4 (9–10): accurate and detailed plan covering IV and operationalised DV, clear matching procedure with random allocation within pairs, several controls, ethics and data analysis; replicable. Level 3 (6–8): most features with some detail. Level 2 (3–5): basic plan with matching mentioned but vague. Level 1 (1–2): little relevant detail. Max 4 if design is not matched pairs.
(b) Weakness: matching only on digit span leaves other participant variables, such as anxiety, unmatched. Improvement: also measure anxiety with a short rating scale and match on both, or use repeated measures with two equivalent digit lists and counterbalancing.
1 mark weakness; 1 mark explanation; 1 mark improvement; 1 mark why improvement helps.
Q16Experimental designs · Challenge · Paper 2 style · 6 marks
A hypothetical repeated measures experiment tests reading comprehension (score out of 25) with phone notifications switched off (condition A) or on (condition B). The order was counterbalanced.Order 1 (A then B): A scores 18, 16, 19, 17, 20; B scores 14, 13, 15, 12, 16Order 2 (B then A): B scores 11, 12, 10, 13, 14; A scores 19, 20, 18, 21, 22
(a)Calculate the mean score for condition A and for condition B, using all ten participants.[2]
(b)Using the data, explain whether there is evidence of an order effect.[3]
(c)Explain why the researcher can still draw a conclusion about the IV.[1]
(b) Yes, a practice effect: condition A mean was 18 when done first and 20 when done second; condition B mean was 12 when done first and 14 when done second, so each condition scored 2 more when done second.
1 mark: A first 18 vs second 20; 1 mark: B first 12 vs second 14; 1 mark: names practice effect / both improve when second.
(c) Because the design was counterbalanced, the practice effect was spread equally over both conditions, so the 6-point difference between A and B is still due to the notifications.
1 mark.
Q17Experimental designs · Challenge · Paper 2 style · 4 marks
A hypothetical experiment tests whether students in a school in Accra understand a passage better when it is printed on paper or shown on a tablet.
(a)Compare the repeated measures and independent measures designs for this study, and explain which you would recommend.[4]
Show answer
(a) Repeated measures removes differences in reading ability between conditions and needs half as many students, but students would read two passages and could guess the aim or improve with practice; independent measures avoids order effects and guessing, but differences in reading ability between groups could confound the result. Recommendation: repeated measures with two passages of equal difficulty and counterbalancing, because reading ability varies widely between students and is the biggest threat to validity.
1 mark repeated strength; 1 mark repeated weakness; 1 mark independent strength/weakness; 1 mark justified recommendation.
Q18Controls and standardisation · Core · Paper 2 style · 3 marks
(a)Explain what is meant by 'standardisation' in an experiment.[1]
(b)A hypothetical experiment tests whether colour of ink (red or blue) affects how well students in Multan remember a list of words. Give two ways the procedure could be standardised.[2]
Show answer
(a) Keeping the procedure, instructions and conditions the same for every participant.
1 mark.
(b) Every participant is given the same list of 20 words printed in the same font size; every participant gets exactly 2 minutes to study the list (also: same instructions, same room).
1 mark each, linked to the study.
Q19Controls and standardisation · Core · Paper 2 style · 3 marks
(a)Explain the purpose of a control condition in an experiment.[2]
(b)A hypothetical study tests whether a 10-minute meditation app reduces exam anxiety in Karachi students. Suggest a suitable control condition.[1]
Show answer
(a) It provides a baseline in which the IV is absent, so the experimental condition can be compared with it to see whether the IV had an effect.
1 mark baseline/no IV; 1 mark for comparison.
(b) Students listen to a 10-minute recording of neutral information (e.g. a weather report) through the same app at the same time.
1 mark (same length / same setting, no meditation).
Q20Controls and standardisation · Core · Paper 2 style · 2 marks
(a)In a hypothetical memory experiment, all participants see the same 20 pictures. Explain why the researcher presents the pictures in a different random order to each participant.[2]
Show answer
(a) Pictures near the start and end of a list are usually remembered better; randomising the order stops particular pictures always benefiting from their position, so position does not bias the results.
1 mark position effects; 1 mark randomising spreads them out.
Q21Controls and standardisation · Core · Paper 2 style · 2 marks
(a)In a hypothetical study, the same researcher read the same script to every participant in a calm, neutral voice. Explain why.[2]
Show answer
(a) To standardise the procedure: different researchers or tones of voice could affect participants' behaviour (experimenter effect), which would be an extraneous variable.
1 mark standardisation; 1 mark avoids experimenter effects.
Q22Controls and standardisation · Standard · Paper 2 style · 4 marks
A hypothetical experiment in Ankara tests whether a cup of coffee increases alertness in the afternoon. Alertness is measured by a reaction-time test.
(a)Explain why the researcher should include a placebo condition.[2]
(b)Describe how a double-blind procedure could be used in this study.[2]
Show answer
(a) Participants who know they have had caffeine may expect to feel more alert and try harder; a placebo (decaffeinated coffee that looks and tastes the same) controls for these expectations, so any difference is due to caffeine itself.
1 mark expectations / demand characteristics; 1 mark placebo isolates effect of caffeine.
(b) A colleague prepares coded cups so that neither the participants nor the researcher who gives the drinks and measures alertness knows which cups contain caffeine until all the data are collected.
1 mark participants unaware; 1 mark researcher unaware (with method).
Q23Controls and standardisation · Standard · Paper 2 style · 4 marks
(a)Write a set of standardised instructions for participants in a hypothetical experiment in which they solve anagrams under time pressure.[3]
(b)Explain why standardised instructions are important.[1]
Show answer
(a) 'You will be shown 15 jumbled words, one at a time, on the screen. Rearrange the letters to make a real English word and type it in the box. You have 20 seconds for each word. If you cannot solve one, press Next. Please work alone and do not use your phone. You may stop at any time. Press Start when ready.'
1 mark task explained; 1 mark time limit/what to do if stuck; 1 mark clear, neutral, includes right to withdraw; must not reveal the hypothesis.
(b) So all participants receive the same information and differences in the DV are not caused by differences in what they were told.
1 mark.
Q24Controls and standardisation · Standard · Paper 2 style · 6 marks
(a)Describe controls and standardisation, using any examples.[6]
Show answer
(a) Controls are ways of keeping extraneous variables from affecting the DV, so that only the IV changes, e.g. keeping room temperature, noise and time of day the same, using a control group or placebo, random allocation, counterbalancing. Standardisation is a type of control in which the procedure is identical for everyone, e.g. the same instructions read from a script, the same materials and timing. Both increase validity (the effect is due to the IV) and reliability (the study can be repeated).
Up to 3 marks each: description (1), example (1), why it matters (1).
Q25Controls and standardisation · Standard · Paper 2 style · 4 marks
(a)Explain why it is harder to control variables in a field experiment than in a laboratory experiment.[2]
(b)A hypothetical field experiment in a park in Lahore tests whether a dog increases the number of people who smile at a walker. Suggest two controls the researcher could use.[2]
Show answer
(a) In a natural setting the researcher cannot control things like noise, crowds or weather, which may vary between conditions, whereas a lab lets these be kept the same.
1 mark: real setting variables vary; 1 mark: contrast with lab.
(b) The same walker, wearing the same clothes, walks the same 200 m path at the same time of day in both conditions; trials are done only on dry days.
1 mark each.
Q26Controls and standardisation · Standard · Paper 2 style · 4 marks
A hypothetical experiment in Dhaka tests whether children who learn spelling with tablets do better than children who learn with books. The researcher believes tablets are better and personally tests every child.
(a)Explain how the researcher's expectations could affect the results.[2]
(b)Suggest two controls that would reduce this experimenter effect.[2]
Show answer
(a) The researcher may unconsciously give more encouragement or extra time to the children with tablets, making their scores higher because of the researcher's behaviour rather than the tablets.
1 mark unconscious bias / cues; 1 mark effect on scores.
(b) Give instructions by a recording; have the tests marked by someone who does not know which group each child was in (blind marking).
1 mark each.
Q27Controls and standardisation · Standard · Paper 2 style · 4 marks
A hypothetical study at a bird sanctuary in Sindh records how often parrots interact with two types of enrichment toy (a puzzle feeder or a hanging rope).
(a)Suggest two controls the researcher should use when observing the parrots.[2]
(b)Explain why controlling the time of observation is important.[2]
Show answer
(a) Observe at the same time each day (e.g. 30 minutes after the morning feed); use the same observer standing at the same distance behind a screen so the birds are not disturbed.
1 mark each, in context.
(b) Birds are more active at certain times (e.g. early morning, before feeding), so observing at different times in different conditions could change the number of toy interactions regardless of the toy type.
1 mark activity varies with time; 1 mark confound.
Q28Controls and standardisation · Standard · Paper 2 style · 4 marks
A hypothetical experiment tests whether a radio advert for a juice drink is more persuasive when it uses a famous singer's voice or an unknown person's voice. Participants rate how much they want to buy the drink from 1 to 10.
(a)Give two variables, other than the IV, that should be kept the same in the two conditions.[2]
(b)Explain why the researcher should allocate participants to the conditions randomly.[2]
Show answer
(a) The length and content of the advert / the volume at which it is played; the room and time of day (also: the same products shown on the rating sheet).
1 mark each.
(b) So that participant variables such as age or liking for the product are spread equally between the conditions, and the researcher does not unconsciously put certain people in one group.
1 mark spread participant variables; 1 mark avoid researcher bias.
Q29Controls and standardisation · Challenge · Paper 2 style · 4 marks
A hypothetical laboratory experiment in Singapore tests whether people change their answers to match others in an online group chat.
(a)Explain how the researcher could use a cover story to reduce demand characteristics.[2]
(b)Explain one ethical problem with using a cover story and how it could be dealt with.[2]
Show answer
(a) Tell participants the study is about which colours people prefer for a new website, so they do not know conformity is being measured and behave naturally when they hear others' answers.
1 mark cover story example; 1 mark explanation of how it reduces demand characteristics.
(b) It is deception, so participants cannot give fully informed consent; they should be debriefed fully afterwards, told the real aim and offered the chance to withdraw their data.
1 mark problem; 1 mark solution.
Q30Controls and standardisation · Challenge · Paper 2 style · 4 marks
(a)Evaluate the use of strict controls in laboratory experiments. Refer to one strength and one weakness.[4]
Show answer
(a) Strength: strict controls (same room, time, instructions) remove extraneous variables, so the researcher can be confident that the IV caused the change in the DV (high internal validity) and the study can be replicated. Weakness: the more controlled the situation, the more artificial it becomes, so participants may behave differently from real life (low ecological validity) and may respond to demand characteristics.
2 marks each: point + explanation (example credited).
Similar questions
Questions that test the same subtopic in different years, grouped so you can work on one skill at a time.
References only: find each question in its paper (official link where available, otherwise through your school).
