7.4: Statistical tests Flashcards
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.
Table 1: Mean number of verbal errors and standard deviations for both conditions, Condition A (believed audience of 5 listeners) had a mean of 11.1 and a standard deviation of 1.30. Condition B (believed audience of 100 listeners) had a mean of 17.2 and a standard deviation of 3.54.
Name an appropriate statistical test that could be used to analyse the number of verbal errors in Table 1. Explain why the test you have chosen would be a suitable test in this case (4 marks)
t-test - can assume interval data because verbal errors can be assumed to be of equal size (ie one verbal error is equivalent to any other verbal error) • the experimental design is independent groups • the psychologist is looking for a difference between the two conditions
or
Mann-Whitney test - data should be treated as ordinal. Cannot assume interval data because verbal errors cannot be assumed to be of equal size (ie one verbal error is not equivalent to any other verbal error) • the experimental design is independent groups • the psychologist is looking for a difference between the two conditions • SDs are quite different
A researcher carried out an overt observation study of social learning. For one week the helping behaviour of children in a playgroup was recorded. All the children then saw a short film in which a child was praised for tidying up toys. For the following week the helping behaviour of the same children in the playgroup was recorded.
At the end of the observation study the researcher used a sign test to see if the behaviour of the children was more helpful, less helpful or the same after seeing the film than it was before they had seen the film.
Explain why the researcher decided the sign test would be an appropriate statistical test to use on the data from this study (4 marks)
The researcher decided the sign test would be an appropriate statistical test to use on the data from this study, because the researcher is looking for a difference in helping behaviour and doing a sign test is one way in which the analysed data would show such a difference
A researcher carried out an overt observation study of social learning. For one week the helping behaviour of children in a playgroup was recorded. All the children then saw a short film in which a child was praised for tidying up toys. For the following week the helping behaviour of the same children in the playgroup was recorded.
At the end of the observation study the researcher used a sign test to see if the behaviour of the children was more helpful, less helpful or the same after seeing the film than it was before they had seen the film.
Explain why the researcher decided the sign test would be an appropriate statistical test to use on the data from this study (4 marks).
The researcher decided the sign test would be an appropriate statistical test to use on the data from this study, because the researcher is looking for a difference in helping behaviour and doing a sign test is one way in which the analysed data would show such a difference.
What did the study focus on?
The study focused on a single group of children who were tested under both conditions
A researcher carried out an overt observation study of social learning. For one week the helping behaviour of children in a playgroup was recorded. All the children then saw a short film in which a child was praised for tidying up toys. For the following week the helping behaviour of the same children in the playgroup was recorded.
At the end of the observation study the researcher used a sign test to see if the behaviour of the children was more helpful, less helpful or the same after seeing the film than it was before they had seen the film.
Explain why the researcher decided the sign test would be an appropriate statistical test to use on the data from this study (4 marks).
The researcher decided the sign test would be an appropriate statistical test to use on the data from this study, because the researcher is looking for a difference in helping behaviour and doing a sign test is one way in which the analysed data would show such a difference.
The study focused on a single group of children who were tested under both conditions – what?
The study focused on a single group of children who were tested under both conditions – the sign test can only be used with one group of participants/repeated measures design
A researcher carried out an overt observation study of social learning. For one week the helping behaviour of children in a playgroup was recorded. All the children then saw a short film in which a child was praised for tidying up toys. For the following week the helping behaviour of the same children in the playgroup was recorded.
At the end of the observation study the researcher used a sign test to see if the behaviour of the children was more helpful, less helpful or the same after seeing the film than it was before they had seen the film.
Explain why the researcher decided the sign test would be an appropriate statistical test to use on the data from this study (4 marks).
The researcher decided the sign test would be an appropriate statistical test to use on the data from this study, because the researcher is looking for a difference in helping behaviour and doing a sign test is one way in which the analysed data would show such a difference.
The study focused on a single group of children who were tested under both conditions – the sign test can only be used with one group of participants/repeated measures design.
What will using a sign test allow the researcher to do?
Using a sign test will allow the researcher to decide whether differences in helping behaviour are due to chance factors or a ‘real’ effect
A researcher carried out an overt observation study of social learning. For one week the helping behaviour of children in a playgroup was recorded. All the children then saw a short film in which a child was praised for tidying up toys. For the following week the helping behaviour of the same children in the playgroup was recorded.
At the end of the observation study the researcher used a sign test to see if the behaviour of the children was more helpful, less helpful or the same after seeing the film than it was before they had seen the film.
Explain why the researcher decided the sign test would be an appropriate statistical test to use on the data from this study (4 marks).
The researcher decided the sign test would be an appropriate statistical test to use on the data from this study, because the researcher is looking for a difference in helping behaviour and doing a sign test is one way in which the analysed data would show such a difference.
The study focused on a single group of children who were tested under both conditions – the sign test can only be used with one group of participants/repeated measures design.
Using a sign test will allow the researcher to decide whether differences in helping behaviour are due to chance factors or a ‘real’ effect.
This study produces quantitative/numerical data and the sign test is one way of analysing such data
Researchers used a test to measure the mathematical reasoning ability of pairs of identical and non-identical twins. If both members of a pair had a similar score on
the test, they were said to be ‘concordant’. This type of study is known as a concordance study.
Outcome of the research with the concordance rates expressed as a percentage:
The concordance rate for mathematical reasoning ability for the genetic relationship group of identical twins (100% shared genes) was 58%.
The concordance rate for mathematical reasoning ability for the genetic relationship group of non-identical twins (50% shared genes) was 14%.
Some ways of establishing validity involve the use of a statistical test.
Outline how these researchers could have used a statistical test to establish concurrent validity of the mathematical reasoning ability test (4 marks)
- Concurrent validity would involve correlating the results on the maths test with results for the same group of people on an established maths reasoning test
- A Spearman’s rho or Pearson’s r test should be used for the two sets of testresults
- If the mathematical ability test is valid then there should be a significant positive correlation between the two sets of test scores at the 0.05 level
A researcher wanted to see whether cognitive behaviour therapy was an effective treatment for depression.
Twenty depressed patients who had all recently completed a course of cognitive behaviour therapy were involved in the investigation.
From their employment records, the researcher kept a record of the number of absences from work each patient had in the year following their treatment.
This was compared with the number of absences from work each patient had in the year prior to their treatment.
Those patients who had fewer absences from work in the year following their treatment than in the year prior to their treatment were classified as ‘improved’ (+).
Those patients who had more absences were classified as ‘deteriorated’ (-).
Those patients who had the same number of absences were classified as ‘neither’ (0).
The researcher decided to use the sign test to analyse the data.
Explain two factors that the researcher had to take into account when deciding to use the sign test (4 marks).
Refer to the investigation in your answer
One factor is nominal data
A researcher wanted to see whether cognitive behaviour therapy was an effective treatment for depression.
Twenty depressed patients who had all recently completed a course of cognitive behaviour therapy were involved in the investigation.
From their employment records, the researcher kept a record of the number of absences from work each patient had in the year following their treatment.
This was compared with the number of absences from work each patient had in the year prior to their treatment.
Those patients who had fewer absences from work in the year following their treatment than in the year prior to their treatment were classified as ‘improved’ (+).
Those patients who had more absences were classified as ‘deteriorated’ (-).
Those patients who had the same number of absences were classified as ‘neither’ (0).
The researcher decided to use the sign test to analyse the data.
Explain two factors that the researcher had to take into account when deciding to use the sign test (4 marks).
Refer to the investigation in your answer.
One factor is nominal data, why?
One factor is nominal data, as the patients are assigned to one of 3 categories - ‘Improved’, ‘deteriorated’ or ‘neither’
A researcher wanted to see whether cognitive behaviour therapy was an effective treatment for depression.
Twenty depressed patients who had all recently completed a course of cognitive behaviour therapy were involved in the investigation.
From their employment records, the researcher kept a record of the number of absences from work each patient had in the year following their treatment.
This was compared with the number of absences from work each patient had in the year prior to their treatment.
Those patients who had fewer absences from work in the year following their treatment than in the year prior to their treatment were classified as ‘improved’ (+).
Those patients who had more absences were classified as ‘deteriorated’ (-).
Those patients who had the same number of absences were classified as ‘neither’ (0).
The researcher decided to use the sign test to analyse the data.
Explain two factors that the researcher had to take into account when deciding to use the sign test (4 marks).
Refer to the investigation in your answer.
One factor is nominal data, as the patients are assigned to one of 3 categories - ‘Improved’, ‘deteriorated’ or ‘neither.’
Another factor
Another factor is the repeated measures design
A researcher wanted to see whether cognitive behaviour therapy was an effective treatment for depression.
Twenty depressed patients who had all recently completed a course of cognitive behaviour therapy were involved in the investigation.
From their employment records, the researcher kept a record of the number of absences from work each patient had in the year following their treatment.
This was compared with the number of absences from work each patient had in the year prior to their treatment.
Those patients who had fewer absences from work in the year following their treatment than in the year prior to their treatment were classified as ‘improved’ (+).
Those patients who had more absences were classified as ‘deteriorated’ (-).
Those patients who had the same number of absences were classified as ‘neither’ (0).
The researcher decided to use the sign test to analyse the data.
Explain two factors that the researcher had to take into account when deciding to use the sign test (4 marks).
Refer to the investigation in your answer.
One factor is nominal data, as the patients are assigned to one of 3 categories - ‘Improved’, ‘deteriorated’ or ‘neither.’
Another factor is the repeated measures design, why?
Another factor is the repeated measures design, as the same patients’ work records are compared before and after treatment
