PSYC2012 – PSYCHOLOGY: AN EVIDENCE-BASED APPROACH 2
ASSESSMENT 2: Data Analysis Assignment
You have been provided with the data for this assignment as an SPSS file. The data file has been provided with generic variable names (V1, V2, etc.), which you should change. You will need to provide more detailed VARIABLE LABELS and VALUE LABELS in the data file.
The hypothetical study examines the relationship between body mass index (BMI), sex, and different measures of response inhibition, delay of gratification, and positive/negative affect. The researchers recruited 120 adults and recorded their sex (V1: 1 = female; 2 = male) and BMI (V2: 1 = underweight; 2 = normal; 3 = overweight). Participants reported their level of hunger (V3) – at the start of the study – on a Likert scale ranging from 1 = “not hungry at all” to 9 = “extremely hungry”.
Participants then completed a range of self-report measures:
- Kirby Monetary Choice Questionnaire: 27 items, each presenting two choices: either an immediate reward (e.g., “$55 today”) or a larger delayed reward (e.g., “$75 in 61 days”). The higher the overall score (V4), the more likely is the person to choose the smaller, immediate rewards.
- Brief Sensation Seeking Scale: 8 items, scored on a Likert scale from 1 = “strongly disagree” to 5 = “strongly agree”. Example item: “I like wild parties”. The higher the overall score (V5), the more likely is the person to seek novel and stimulating experiences.
- The Tightwad-Spendthrift Scale: 4 items, scored using either a 1-11 (item no.1) or 1-5 (items 2-4) ratings. The higher the score (V8), the more difficultly people have in controlling their spending. Tightwads (i.e., those with low scores), on the other hand, tend to become anxious and experience pain when they have to spend money.
- The Positive and Negative Affect Schedule – Expanded form (PANAS-X): Participants are presented with a list of 60 adjectives (e.g., confident, joyful, upset, angry), and are asked to indicate the degree to which they feel each of these positive and negative emotional states in general. Items are scored on a Likert scale ranging from 1 = “very slightly or not at all” to 5 = “extremely”. V9 indicates positive and V10 negative affect scores. High scores on V9 and V10 represent high levels of positive and negative affect, respectively.
Finally, participants completed a Go/No-Go task, which measures inhibitory control. A Go/No-Go task presents two stimuli; one is a “go” target to which participants are instructed to respond as fast as they can (e.g., by pressing spacebar on a keyboard), and the other is a “no-go” target to which one must withhold responses. Failure to withhold responses to no-go targets is known as a commission error. The lower the commission error, the better is the inhibitory control. The current study used happy and sad faces as the stimuli. In the first half of the task, happy faces were the go and sad faces were the no-go targets. In the second half, the sad faces became the go while the happy faces were the no-go targets. Previous literature suggests those with reduced inhibitory control find it more difficult to resist responding to happy than sad faces. V6 represents commission errors to happy no-go targets, and V7 commission errors to sad no-go targets.
Your first task is to provide appropriate variable labels for all the variables and value labels for V1 (sex) and V2 (BMI). After this, answer the following questions. You must provide the relevant SPSS output along with any write-up that is requested. Any figures or tables must be in APA style. You are not required to interpret any of the results in “common sense” terms. The exercise is solely related to the data analysis, and the variables and their scores are somewhat arbitrary, so don’t worry if the results don’t make “real world” sense. This is not real data, so don’t worry if the results seem odd.
There are two parts to this report. The most important part consists of the write up of the analyses, including graphs and tables (if required) in correct APA style; in other words, in the style that you would use if you were presenting this material in a research report. The second part consists of the raw SPSS output of the analysis that you have carried out. Both sections need to be combined into a single Word file for submission to the online class space. Remember that SPSS provides a lot of output. Not all of this output needs to be submitted with your assignment. You should copy and paste only part of the output that directly relates to the question that you are answering.
Please note that you are required to answer ALL SIX questions. Each question worth 5 marks.
- Examine all the variables from V3 to V10 for any violations of the normality assumption. Pick a variable that you feel violates the assumption. Run at least three transformations on that variable, and then make a decision as to which transformed version leads to the best improvement. If none of the transformed versions leads to any improvement (i.e., meet the assumption of normality), then continue to use the original variable. Write up the procedure you followed for that one variable (ignore the others that you tested) in the form that you would write it up were it part of a research report. For all of the remaining questions, use the transformed variable (assuming that you decide that the transformed variable is an improvement on the original; otherwise, stick with the original).
- Test the homogeneity of variance assumption on variables V3 to V10, with variable V2 as the grouping variable/factor. Pick one variable that you feel violates the assumption and run the appropriate power transformation on that variable. Write up the procedure you followed for that one variable (ignore the others that you tested) in the form that you would write it up were it part of a research report. For all of the remaining questions, use the transformed variable (assuming that you decide that the transformed variable is an improvement on the original (i.e., using the transformed variable, the assumption is met); otherwise, stick with the original)
- Carry out a contingency table analysis using c2 to answer the question of whether there is a significant relationship between sex and BMI. In other words, are males and females equally represented across the three BMI groups? Show a bar chart of this relationship and present the descriptive statistics in a properly formatted APA table. Make sure that after running the c2 analysis you use the standardised residuals to help interpret the result.
- Is there a sex difference for the scores on the Kirby Monetary Choice Questionnaire (V4)? Is there a sex difference on Brief Sensation Seeking Scale (V5)? Write up the results in APA style, including properly formatted APA-style graphs of the means and an APA style table of the descriptive results (you can provide the results for both variables in the one table or in separate tables). Two separate analyses and two graphs are required for this question, and at least one table.
- Show a correlation matrix of the eight continuous variables, with significance levels. Present the matrix as a properly formatted APA-style table, then pick two significant correlations from the matrix and write up these results in APA style.
- Is there a significant difference between commission errors to happy (V6) and sad faces (V7)? Pick an appropriate significance test to answer this question, and present the results in APA style, along with a properly formatted APA bar chart and a table of the descriptive results.
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The report is worth 30% of your grade for this unit.
Marking Guide
Each question will be marked out of five, giving a total grade out of 30.
- A grade of 4 – 5 will be given for an answer that is of High Distinction standard
- A grade of 3.5 will be given to an answer that is of Distinction standard
- A grade of 3 will be given to an answer that is of Credit standard
- A grade of 2.5 will be given to an answer that is of Pass standard
- Answers that fail will be given a grade < 2.5
Each question will be assessed holistically, taking into account the following aspects:
- Accuracy of data analysis; that is, have the correct procedures been used to answer each question.
- Correct reporting of each analysis; that is, have the correct conclusions been reached, and accurately reported.
- Adherence to APA style in all respects.
- Where tables and/or figures have been reported, are they in correct APA style?
The following overall guidelines will sit atop these criteria when assigning a final grade:
HD Outstanding work in terms of originality, understanding, interpretation and presentation.
DI A very high standard of work which demonstrates originality and insight.
CR Demonstrates a higher level of understanding and presentation.
PA Satisfies the minimum requirements for content and presentation.
NN Fails to satisfy the minimum requirements of content and presentation.
