Experiments: Types & Design (AQA A Level Psychology)

The psychologist decided to design an experiment to test the effects of recreational screen time on children’s academic performance.

The psychologist randomly selected four schools from all the primary schools in her county to take part in the experiment involving Year 5 pupils. Three of the four schools agreed to take part. In total, there were 58 pupils whose parents consented for them to participate. The 58 pupils were then randomly allocated to Group A or Group B.

For the two-week period of the experiment, pupils in Group A had no recreational screen time. Pupils in Group B were allowed unrestricted recreational screen time. At the end of the experiment all pupils completed a 45-minute class test, to achieve a test score.

One criticism of the study is that the pupils were not matched on their typical recreational screen time.

Explain how the psychologist could have matched pupils on their typical recreational screen time across the experimental conditions.

Identify one other variable for which the psychologist could have matched the pupils. Explain how this might have affected the test performance if it was not controlled.

In an experiment into the effects of cognitive priming, 20 participants played an unfamiliar computer game. Half of the participants watched a violent film before playing the computer game. The other half watched a neutral film before playing the computer game. After playing the computer game, each participant was classified as showing High Aggression or Low Aggression.

Different participants were used in each condition of the experiment, which might have affected the results.

Explain one way in which the experiment could be changed to control for the problem of using different participants in each condition.

A psychologist wanted to investigate whether exercise would affect stress levels in 15-year-olds. Previous research into the effects of exercise on stress in teenagers had shown that exercise decreased stress levels.

The psychologist decided to use a repeated measures design to investigate the effects of exercise on stress levels in 20 15-year-old students. All the students were approaching their end-of-year exams.

For Condition A, students were required to complete a 2 km run during their morning breaktime each school day for one week.

In Condition B, students continued their normal activities in the playground during their morning breaktime each school day for one week.

At the end of each week of the investigation, for both Condition A and Condition B, each student was asked to rate their levels of stress on a rating scale of 1–10, where the higher the self-reported rating the greater the stress levels.

To improve the validity of the findings, the psychologist counterbalanced the students across the experimental conditions.

Describe how the psychologist could have counterbalanced the students across the experimental conditions.

A psychology teacher read a researcher’s study on sport and happiness. She considered whether setting group tasks could improve her students’ level of happiness. She decided to conduct an independent groups experiment with 30 students taking A-level Psychology using the same happiness questionnaire.

Design an independent groups experiment that the psychology teacher could conduct.

In your answer you should provide details of:

• the aim of the experiment

• identification and manipulation of variables including details of the task

• controls to minimise the effects of extraneous variables

• data handling and analysis – use of descriptive statistics and/or data presentation.

Justify your design choices.

A new TV programme has been developed to increase positive social behaviours in pre-school children.

There is a proposal to carry out an experiment to compare the effects of the new TV programme and an existing TV programme, on positive social behaviours in pre-school children.

A sample of 500 pre-school children and their parents is available for the experiment. The parents have given consent for their children to take part in this experiment.

The experiment will take place over an 8-week period. Data on the children’s social behaviours will be gathered from the parents using a self-report method.

Design the experiment to investigate whether watching the new TV programme leads to an increase in positive social behaviours in the children, compared with watching the existing TV programme.

In your answer you will gain credit for providing appropriate details of the following:

• the type of experimental design, with justification

• a self-report method of data collection, with justification

• how to control one extraneous variable, with justification as to why this would need to be controlled