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Laboratory Experiments

Last updated 22 Mar 2021

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Experiments look for the effect that manipulated variables (independent variables, or IVs) have on measured variables (dependent variables, or DVs), i.e. causal effects.

Laboratory experiments pay particular attention to eliminating the effects of other, extraneous variables, by controlling them (i.e. removing or keeping them constant) in an artificial environment. This makes it more likely for researchers to find a causal effect, having confidence that no variables other than changes in an IV can affect a resulting DV. Laboratory experiments are the most heavily controlled form of experimental research.

Participants can also be randomly allocated to experimental conditions, to avoid experimenter bias (i.e. the experimenter cannot be accused of choosing who will be in each experimental condition, which could affect the results).

Evaluation of laboratory experiments:

- High control over extraneous variables means that they cannot confound the results, so a ‘cause and effect’ relationship between the IV and DV is often assumed.

- Results of laboratory experiments tend to be reliable, as the conditions created (and thus results produced) can be replicated.

- Variables can be measured accurately with the tools made available in a laboratory setting, which may otherwise be impossible for experiments conducted ‘in the field’ (field experiments).

- Data collected may lack ecological validity, as the artificial nature of laboratory experiments can cast doubt over whether the results reflect the nature of real life scenarios.

- There is a high risk of demand characteristics, i.e. participants may alter their behaviour based on their interpretation of the purpose of the experiment.

- There is also a risk of experimenter bias, e.g. researchers’ expectations may affect how they interact with participants (affecting participants’ behaviour), or alter their interpretation of the results.

• Laboratory Experiment

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Example Answers for Research Methods: A Level Psychology, Paper 2, June 2019 (AQA)

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Essential AQA A-Level Psychology Teaching Research Methods

This self-paced AQA A Level Psychology course provides a walkthrough of the entire Research Methods specification.

• 10-20 hours learning time
• 12 course steps

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Access this course and grow in confidence in Research Methods. This course offers you a complete walkthrough and guide to teaching Research Methods, plus advice and suggestions on assessment activities for your lessons.

The course comes complete with worksheets for you to use in class, plus Powerpoints for every part of Research Methods. Also included in this fantastic and comprehensive course, is a range of downloadable teaching, learning, and assessment activities.

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A self-paced CPD course suitable for all teachers of AQA A Level Psychology

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Essential AQA A-Level Psychology

Course outline

• Introduction to Research Methods
• The Scientific Process
• Experimental Methods and Correlations
• Observational Methods
• Self Report Methods
• Reliability and Validity
• Data Analysis
• Inferential Statistics
• Designing Research
• Research Methods Revision
• Exam Question Walkthrough

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Jess has worked as a teacher of psychology for over 15 years and during that time has been a Head of department. In addition, Jess has experience as an examiner for AQA as well as working for Pixl6.

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Laura is Subject Leader for Psychology here at tutor2u. She is an experienced Psychology and Sociology lecturer. Laura is passionate about trying new strategies and reflecting on how to improve. She has worked as an advanced TLA coach and Deputy Head of Sixth Form.

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Preview text, example answers, aqa a level psychology, research methods, workbook edition 2.

####### 2 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

Introduction 3

Top tips for answering research methods questions 4, sample student answer with examiner comments 5, scenario 1: does personality influence degree choice 8, scenario 2: the relationship between age and fine motor, scenario 3: does social media affect self-image 16, scenario 4: how do early relationships influence later, relationships, scenario 5: does the age of a person influence whether, they are helped or not, scenario 6: investigating children’s friendships 28, scenario 7: the stroop effect 32, scenario 8: how alike are separated identical twins 36, scenario 9: what else do people do while watching tv 40.

Read the scenario carefully and underline any key information. Candidates lose marks because they have not read the scenario properly.

Context is vital. If it says ‘in this investigation’, then you MUST contextualise your answers. Generic answers gain very few marks.

Do not confuse experimental methods (lab, field, natural and quasi) with experimental designs (independent groups, repeated measures and matched pairs).

It is very important to understand the difference between sampling techniques used to select participants for a study (e. volunteer sampling) and sampling methods used in observational research (e. event sampling).

Do not confuse findings with conclusions. Findings refer to the actual data found from the participants in the investigation; conclusions refer to what this data tells us about the behaviour of people in general.

When asked to write an experimental hypothesis, both the independent variable (IV) and the dependent variable (DV) need to be fully operationalised for full marks. When asked to write a hypothesis for a correlational study, both co-variables need to be operationalised for full marks.

Do not confuse types of data (qualitative/quantitative) with levels of measurement (nominal/ordinal/interval).

Learn a table, decision tree or mnemonic to help you decide which statistical test to use and why (see below).

Test of Difference Test of Association

Related design unrelated design or correlation, nominal data.

Chi-squared

Ordinal Data

Mann-Whitney

Spearman’s rho

Interval Data

Related t-test (Parametric)

Unrelated t-test (Parametric)

Pearson’s r (Parametric)

####### 4 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

Do category names help people recall more words?

A psychology student read some research in a psychology journal that showed that being given category names helped people to recall more words. She decided to investigate this. She recruited 20 participants from the 200 students in the sixth form at her school. All of the participants were shown the same series of 30 words (6 from each of 5 categories) one at a time on a screen. Each word was presented for one second. The participants were then given a number and asked to count backwards in 3s from it for 30 seconds. Ten participants (the control group) were asked to write down as many of the words as they could in any order. The other ten (the experimental group) were given the 5 categories (animals, fruit, colours, occupations, vehicles) and asked to write down as many of the words as they could in any order. Both groups were given 2 minutes to recall the words.

QUESTION 1 State an operationalised directional hypothesis for this investigation. [3 marks]

Comments: This answer is worth 3 marks because it is directional (says which group will

remember more) and both conditions of the IV (whether they are given the 5 categories or not) and the DV (how many of the 30 words were remembered) are clearly operationalised. When operationalising a variable, you need to include as much detail as you can.

Student Answer: Participants who are given the 5 categories before being asked to recall will remember more of the 30 words than participants who are not given the 5 categories.

Sample answer

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QUESTION 2 Explain why it was appropriate to use a directional hypothesis in this investigation. [2 marks]

Comments: 2 marks as this is an accurate and

detailed answer that is applied to the stimulus material. Please note, you could also be asked whether it is more appropriate to make a directional or a non-directional hypothesis. If this is the case, read the stimulus material carefully to ensure that it refers to peer-reviewed research that has been published in a journal, rather than something that has just been printed in a newspaper or magazine.

Student Answer: It was appropriate for the psychology student to use a directional hypothesis because previous research that had been peer- reviewed and published in a journal had already shown that being given category names improved recall.

####### tutor2u 7

Comments: 2 marks as this answer clearly explains how the random allocation could have taken

place. It also explains the whole procedure from start to finish, which is something candidates often fail to do.

QUESTION 7 Identify one variable that has been controlled in this investigation and explain why it was important to do this. [3 marks]

Student Answer: One variable that has been controlled is the time taken to present each word (1 second). It was important to do this as if some of the words were shown on the screen for longer than others this would have allowed the participants longer to rehearse them, meaning they might have been more likely to remember them.

Comments: This candidate has received 1 mark for correctly identifying a variable that has been

controlled and 2 marks for explaining clearly why it was important to do this.

QUESTION 8 Identify an appropriate statistical test for the student to use to analyse the data. Explain why this would be an appropriate test to use in this investigation. [4 marks]

Student Answer: It would be appropriate for the student to use the Mann Whitney test. This is because she is looking for a difference in the number of words recalled between the group given the category names and the group who were not. She has used an unrelated design (independent groups) as one group of participants saw the category names and the other group did not. The data she has collected is ordinal level. This is because although everyone got a score, some of the words may be easier to remember than others, so we cannot be sure that the measuring scale (score of 1 to 30) has equal distance between the points.

Comments: This answer received 4 marks because the candidate has correctly identified an

appropriate test and has then given 3 reasons for why it would be appropriate. Each reason is clearly applied to the stimulus material. Please note that the related t-test would also have been credited, as long as the candidate explained why they believed the data to be interval level.

QUESTION 9 The psychology student chose the 0 level of probability to avoid making either a Type I or a Type ll error. Distinguish between a Type I and a Type II error in this investigation. [4 marks]

Student Answer: A Type I error is a false positive. It is when you accept your research/ experimental hypothesis when it is false. In this investigation, it would be saying that being given the category names improved recall, when that was not true. Whereas, a type II error is a false negative. It is where you reject the research/experimental hypothesis when it is actually true. In this investigation, it would be saying that being given the category names did not improve recall when it actually did.

Comments: 4 marks as the answer has clearly and accurately distinguished between a Type I and

a Type II error, and has also applied this to the investigation in the scenario. Rather than simply describe what each is, the word whereas demonstrates that there is a difference between them.

####### 8 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

DOES PERSONALITY INFLUENCE DEGREE CHOICE?

A psychologist was interested in carrying out an experiment to see whether students completing a Psychology degree were more or less extrovert than students completing an English degree. She used an opportunity sample of 22 third year students from the university where she lectured and asked them to complete a personality questionnaire, where the higher the score the more extrovert an individual is deemed to be.

There were 11 English students and 11 Psychology students. Each student had a different score for extroversion. The median score for the English students was 15 and the median score for the Psychology students was 18.

QUESTION 1 Explain which experimental method has been used in this investigation. [2 marks]

Answer: A quasi-experiment has been used. This is because the IV is whether the participant is an English student or a Psychology student and this is not being manipulated by the psychologist. It is a difference that already exists.

QUESTION 2 Identify the dependent variable in this investigation. [1 mark]

Answer: The DV is the score on the extraversion questionnaire.

####### 10 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

QUESTION 6 Explain how a matched pairs design could have been used in this investigation. [3 marks]

Answer: A matched pairs design could have been used by the psychologist pairing the English students and the Psychology students on variables that might affect their extroversion score. For example, gender and age. If she allocated a male aged 21 to the Psychology group, then she would also allocate a male aged 21 to the English group. She would do this for all of the participants.

QUESTION 7 Explain one strength of using a matched pairs design in this investigation. [2 marks]

Answer: One strength of using a matched pairs design is that it controls for participant variables. In this investigation variables such as age and gender might influence extroversion scores and by using a matched pairs design these can be controlled so that they do not affect the results.

QUESTION 8 Explain one reason why the psychologist may have chosen to use the median as a measure of central tendency in this investigation. [2 marks]

Answer: They may have chosen to use the median because the extroversion scores for one or both of the groups included extreme values. When this is the case it is better to use the median rather than the mean because it is not affected by anomalies.

####### tutor2u 11

QUESTION 9 How many of the psychology students had a score < the median? [4 marks]

Answer: 5 participants had a score lower than the median. This is because all 11 scores are different and when arranged in numerical order, the 6th score would be the median. This means that 5 participants scored below 18 and 5 scored above.

QUESTION 10 Explain what the median scores suggest about the effects of personality on degree choice. [2 marks]

Answer: The median scores suggest that personality does affect degree choice as the Psychology students had higher scores for extraversion (18) than the English students (15).

QUESTION 11 Explain one limitation of using a personality questionnaire to assess extroversion. [2 marks]

Answer: One limitation of using a personality questionnaire is social desirability bias. The students may have felt that they needed to show themselves to be more outgoing and extrovert than they really were because they believed that to be more socially acceptable.

Exam Hint: If you are asked a question regarding why a particular measure of central tendency has been

used (e. the median or the mean), then there are two things that you need to consider. One is the level of measurement, as the mean should only be used with data that is interval (or ratio) level. If the data is clearly ordinal level (e. ratings), then median is the appropriate measure of central tendency. The other important thing to consider is whether there are any anomalies or extreme scores in the data. If this is the case, then even if the data is at least interval level the median is the most appropriate measure of central tendency.

####### tutor2u 13

QUESTION 2 Explain how the psychologist could have conducted a pilot study prior to this investigation. [4 marks]

Answer: The psychologist could have run a small-scale trial with a small sample of children (maybe one at the top of the age range and one at the bottom). He would run through the procedure with them to check that they could understand the instructions. He would also check that they were able to complete the task and thread the beads onto the string. If he found any problems then these could have been rectified before he completed the investigation.

QUESTION 3 Write a directional hypothesis for this investigation. [3 marks]

Answer: There will be a negative correlation between the age of a child (in months) and the time taken (in seconds) to thread 5 beads onto a piece of string.

Exam Hint: When writing a hypothesis, it is important to make sure that you have followed the

instructions regarding whether it should be directional (one-tailed) or non-directional (two-tailed). If the investigation is an experiment, you need to make sure that you have included both conditions of the independent variable and that both the independent variable and the dependent variable are operationalised. If it is correlational research, then both co-variables should be operationalised. Furthermore, the hypothesis MUST be written in either the present or the future tense because it is a prediction of the outcome of an investigation.

####### 14 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

QUESTION 4 Draw a suitable graphical display for the data in Table 1. Label your graph appropriately. [4 marks]

QUESTION 5 Identify what the data shows regarding the relationship between age and time taken to complete the fine motor skill task. [2 marks]

Answer: The data shows a strong negative correlation between age and time taken to complete the fine motor skill task. As age increases, the time taken to thread the beads onto the string decreases.

QUESTION 7 Explain what is meant by the term concurrent validity. [2 marks]

Answer: Concurrent validity means measuring how well the results of a new test compare to the results of an existing test. If both tests have similar results, then the new test is said to have concurrent validity.

####### 16 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

DOES SOCIAL MEDIA AFFECT SELF-IMAGE?

A psychologist was interested in the effects of social media on self-image. In her first investigation, she asked a sample of 12-year-olds about their use of social media and then asked them to write a short essay about how they felt about themselves. Some of her original sample said that they did not use social media and so she decided to conduct a second investigation where she contacted the non-users again when they were aged 16. She then asked those who were now using social media to complete the same task of writing an essay and compared their essays to the essays that they wrote at age 12, measuring how many positive and negative comments they made about themselves. Her findings are shown in Table 1.

Table 1: Mean number of positive and negative comments about the self, before and after using social media.

Before using social media (age 12)

After using social media (age 16)

Mean number of positive comments

Mean number of negative comments

QUESTION 1 Identify the independent variable in the psychologist’s second investigation. [1 mark]

Answer: The IV is whether the participant has used social media or not.

QUESTION 2 Explain why the psychologists second investigation can be described as a natural experiment? [2 marks]

Answer: It is a natural experiment because the researcher has not manipulated the independent variable. The use of social media was decided by the child and not manipulated by the psychologist. The psychologist has simply been able to measure the dependent variable by assessing the children before and after they began to use social media.

####### tutor2u 17

QUESTION 3 Explain one strength and one limitation of using a natural experiment in this investigation. [4 marks]

Answer: One strength of using a natural experiment in this investigation is that it has high ecological validity. This is because it is investigating something that has actually happened to the child in their everyday life (beginning to use social media) rather than manipulating something artificially.

One limitation of using a natural experiment is that it is impossible to control other variables that might have an effect on the DV. In this investigation there may have been other changes (as well as starting to use social media) that have affected the self-image of the participants. For example, it could be due to age and that 16-year- olds are more self-critical than 12-year-olds.

QUESTION 4 Briefly explain what the mean values in Table 1 suggest about the influence of social media on self-image. Justify your answer. [4 marks]

Answer: The mean scores show that the participants made a higher number of critical comments about themselves after they had used social media (6), than before (2). This suggests that social media has a negative influence on self-image.

However, the mean scores also show that the participants also made a higher number of positive comments about themselves after they had used social media (4), than before (3). This suggests that using social media can have a positive effect on self-image too, but this effect is not as great as the difference is smaller (1) than for negative comments (3).

QUESTION 5 Explain how the psychologist could have used content analysis to measure the number of positive and negative comments in the essays. [4 marks]

Answer: The psychologist needed to decide what constituted positive comments and what constituted negative comments by reading through the essays. Examples of positive comments might include sentences such as, ‘I am good at English’ or ‘I am kind’; examples of negative comments would be sentences like, ‘I don’t like my nose’ or ‘I am not as clever as my friends’. Using a tally chart, the psychologist would then work through each essay. When the psychologist had finished going through an essay, the number of negative and positive comments would be added up for that participant.

####### tutor2u 19

####### 20 AQA A LEVEL PSYCHOLOGY RM WORKBOOK

HOW DO EARLY RELATIONSHIPS INFLUENCE LATER ATTACHMENTS?

A psychologist was interested in finding out how the early relationships a mother has affect her attachment to her own infant. He decided to conduct some unstructured interviews with a volunteer sample of 10 mothers. The interviews were recorded and then analysed.

QUESTION 1 Explain one reason why there might be a problem with bias and generalisation in this study. How could the psychologist modify his study to deal with this problem? [4 marks]

Answer: There may be a problem with bias and generalisation as the psychologist has used a volunteer sample, and it is possible that the mothers who volunteered had better early relationships with their infants than mothers who did not volunteer. This means it would not be appropriate to generalise the findings regarding whether the early relationships that mothers have affect their attachments to their own babies, to other mothers of young infants. This study could be modified by using a random sample of mothers with young infants, as this should produce a less biased and more representative sample, meaning that the findings could be generalised more widely.

QUESTION 2 Explain why the psychologist may have chosen to use unstructured rather than structured interviews in this investigation. [3 marks]

Answer: The psychologist may have chosen to use unstructured interviews as they would allow him to have a free-flowing discussion regarding the mother’s early childhood and the relationship she has with her own infant, rather than having to ask a fixed set of questions, as in a structured interview. This would allow the psychologist to be more flexible and to follow-up on points about the mother’s early relationships in order to gain a greater insight into the effects they may be having on her attachment with her infant.

Exam Hint: When you are asked to explain why a researcher has chosen to do

one thing (e. use unstructured interviews) rather than a different thing (e. use structured interviews), it is very important to make reference to both in your answer so that there is a clear comparison and explanation for why the one they chose was more suitable.

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Subject : Psychology

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The Experimental Method

Psychologists carry out experiments both in the laboratory and in the field (the outside world).

Both methods involve the manipulation of an independent variable (iv) and the measurement of a dependent variable (dv).

Experimental method is more controlled than other methods allowing Psychologists to claim that behaviour is a result of the independent variable. (cause and effect)

• Manipulation of the independent variable under controlled conditions allows  cause and effect  to be inferred, although there is less control in field experiment.
• Easy to replicate  due to standardised procedure
• More accurate data collected
• Data is  more objective  than other methods

Disadvantages

• Experiments are  artificial environments  which may produce artificial behaviour.
• Field experiments  are less artificial and therefore they are  more ecologically valid .
• Ethical Problems  over deception, consent, invasion of privacy, potential harm etc.