Summer 2000

Section D - Research Methods in Psychology

Answer questions in this section.

Research investigations in psychology consist not only of experimental investigations carried out in the laboratory and in the field, but also of a wide range of quasi-experimental and non-experimental methods of investigation including natural experiments, naturalistic observational studies and interviews.

(a)     Explain what is meant by the term quasi-experimental (line 2).                (2 marks)

(b)     Describe how a natural experiment differs from a field experiment.             (2 marks)

(c)      Describe two advantages of natural experiments as a research method.    (4 marks)

In a laboratory experiment on the role of interference in attention, a group of participants was asked to state how many letters or digits there were in sequences such as the following:

AAAA          (correct answer = 4)

555555         (correct answer = 6)

The researchers expected that the participants would take longer to respond to the number sequences as the printed numbers conflicted with the number of digits in each of the sequences. Twenty sequences of letters were used and twenty of numbers (in which the number of items in the sequence was always different from the printed number). The lengths of the sequences used in the two conditions were matched.

The researchers used a repeated measures design and the sets of letter and number sequences were presented to participants in counterbalanced order. The times taken to state the number of items for each set of sequences were recorded.

From the results gained from 20 participants, the researchers made the following calculations:

Data were also represented as a frequency polygon (Figure 1).

Number of

Participants

                                                                    Time taken to read sequence

                                Frequency polygon showing the times taken by participants for each condition

                                                                   Figure 1

(a)     Explain one advantage of using a repeated measures design in this study.         (2 marks)

(b)     State an appropriate null hypothesis for this investigation.                                (2 marks)

(c)     Identify the independent variable in this investigation.                                        (1 mark)

(d)     Explain why counterbalancing was used in this investigation.                             (2 marks)

(e)    The researchers were aware that demand characteristics might create problems in an experiment              such as this. Describe one way in which demand characteristics might have affected the results of this investigation.                                                                                                            (2 marks)

(f)     Explain how the two standard deviation values in the table above might be interpreted.                                                                                                                                    (2 marks)

(g) Explain how the information in Figure 1 can be interpreted in terms of the differences between the two conditions. (2 marks)

(h) The researchers used a Wilcoxon Matched Pairs Signed Ranks Test to analyse their data further. State three possible reasons for selecting this test in this investigation.                                 (3 marks)