Data Handling: Descriptive Statistics & Computation (AQA A Level Psychology)

A psychologist wanted to test whether listening to music improves running performance.

The psychologist conducted a study using 10 volunteers from a local gym. The psychologist used a repeated measures design. Half of the participants were assigned to condition A (without music) and half to condition B (with music).

All participants were asked to run 400 metres as fast as they could on a treadmill in the psychology department. All participants were given standardised instructions. All participants wore headphones in both conditions. The psychologist recorded their running times in seconds. The participants returned to the psychology department the following week and repeated the test in the other condition.

The results of the study are given in Table 1 below.

Table 1 Mean number of seconds taken to complete the 400m run and the standard deviation for both conditions

What do the mean and standard deviation values in Table 1 suggest about the participants’ performances with and without music? Justify your answer.

Calculate the percentage decrease in the mean time it took participants to run 400 metres when listening to music. Show your workings. Give your answer to three significant figures.

A psychologist decided to conduct an experiment to investigate the effect of watching horror films before going to bed.

A volunteer sample of 50 university students consented to take part in the experiment.

The 50 students were randomly split into two groups. Group 1 watched a horror film before going to bed each night for the first week then a romantic comedy before going to bed each night for the second week.

Group 2 watched the romantic comedy in the first week and the horror film in the second week. When the students woke up each morning, each student received a text message that asked if they had had a nightmare during the night. They could respond ‘yes’ or ‘no’.

The psychologist collated the responses of all the participants over the two-week period and calculated the mean and standard deviation for each condition.

Table 1 Mean number of nightmares reported and the standard deviation for each condition

What do the mean and standard deviation values in Table 1 suggest about the effect of the type of film watched on the occurrence of nightmares? Justify your answer.

A 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.

The results obtained from the experiment are summarised in Table 1.

Table 1 Descriptive statistics for the test performance scores for Group A and Group B

What do the mean and standard deviation values in Table 1 suggest about the effect of recreational screen time on test performance? Justify your answer.

Researchers studied therapies for schizophrenia. They assessed the mood of two groups of participants before the participants received therapy. The same participants were assessed again after four weeks of receiving therapy.

Group 1 (Drug therapy group) received drug therapy alone.

Group 2 (Combined therapy group) received a combination of drug therapy and cognitive therapy.

The researchers assessed mood using a standardised test of mood. A low score indicated negative mood and a high score indicated positive mood. Scores ranged from 0 to 100. The lowest score was 24 and the highest score was 83.

Table 1 shows the results of the study after four weeks of therapy.

Table 1 Mean mood scores for Group 1 (Drug therapy group) and Group 2 (Combined therapy group) after four weeks of therapy

Explain why the data in Table 1 does not enable the researchers to draw proper conclusions about the effectiveness of therapy for the two groups. What should the researchers do about this?

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 2km 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.

The psychologist calculated the median and range of stress ratings after each condition. This data is presented in Table 1.

What do the median and range values presented in Table 1 suggest about the students’ stress ratings after each condition Justify your answer.

Explain one limitation of using the range to represent the spread of stress ratings.

Researchers were interested in the spatial awareness skills of motorists. They decided to investigate a possible relationship between different aspects of spatial awareness. Motorists who had between ten and twelve years of driving experience and held a clean driving licence with no penalty points were asked to complete two sets of tasks.

Set 1: To follow a series of instructions and using a map, to identify various locations correctly. This provided a map reading score for each motorist with a maximum score of 20.

Set 2: To complete a series of practical driving tasks accurately. This involved tasks such as driving between cones, driving within lines and parking inside designated spaces. Each motorist was observed completing the Set 2 tasks by a single trained observer who rated each performance by giving the driver a rating out of 10.

When the researchers looked at the data collected more closely they noticed possible gender differences in the results.

What do the mean and standard deviation values suggest about the male and female performances in the investigation?

A psychologist wanted to see if verbal fluency is affected by whether people think they are presenting information to a small group of people or to a large group of people.

The psychologist needed a stratified sample of 20 people. She obtained the sample from a company employing 60 men and 40 women.

The participants were told that they would be placed in a booth where they would read out an article about the life of a famous author to an audience. Participants were also told that the audience would not be present, but would only be able to hear them and would not be able to interact with them.

There were two conditions in the study, Condition A and Condition B.

Condition A: 10 participants were told the audience consisted of 5 listeners.

Condition B: the other 10 participants were told the audience consisted of 100 listeners.

Each participant completed the study individually. The psychologist recorded each presentation and then counted the number of verbal errors made by each participant.

The results of the study are given in Table 1.

Table 1: Mean number of verbal errors and standard deviations for both conditions

What conclusions might the psychologist draw from the data in Table 1? Refer to the means and standard deviations in your answer.

The psychologist had initially intended to use the range as a measure of dispersion in this study but found that one person in Condition A had made an exceptionally low number of verbal errors.

Explain how using the standard deviation rather than the range in this situation, would improve the study.