Analysis of Variance Assignment

Weight: 20% of total mark for the unit Due date: Friday 21st Oct 11:59pm Word limit: strictly 1000 words (penalties apply for exceeding this)

General overview: Your task is to design, ‘conduct’, analyse and write a brief report based on the analyses for a research study, following APA guidelines. You will invent your own theoretical rationale for the investigation, and test specific hypotheses (based on the contrast coefficients provided below).

Step 1: Design your study

Design a between-subjects study with two levels on one independent variable (IVA) and four levels on the other (IVB), i.e., a 2 × 4 design. You can be as creative as you wish – it may be set in the distant past/future, under the sea or on a make-believe planet – but it should be of interest to a psychologist. For at least one of the independent variables, participants must be randomly allocated to conditions; that is, only one of the independent variables can be a classification variable (you cannot use gender or age – you need to be more creative than that). Clearly define your dependent variable, which must be measured in whole numbers (i.e., no decimal places) and have a range of 0-50.

In designing the study, you must set theoretically meaningful contrasts before collecting the data, which will be tested by the contrast coefficients below. Your contrasts must adhere to the following:

The interaction contrasts should follow from the main-effect contrasts.
Do not design trend hypotheses – these are not trend contrasts.
You cannot use examples from lectures or tutorials.

Main effect contrast coefficients:

Step 2: ‘Collect’ your data

Once you have designed your study, you will “collect” sample data which has been obtained for you from an appropriate population by an independent participant recruitment company (i.e., you are free to specify any population of interest relevant to your study). Once recruited, participants were allocated to one cell in the study design such that there were equal number of participants in each cell of the study.

If you do not use the data allocated to you, you will receive a 20-mark penalty.

Step 3: Statistical analyses

Use the appropriate syntax in SPSS to test all main-effect contrasts and all interaction contrasts that follow from them. Write up the results for your chosen contrasts (including non-significant ones) in the Results section of your report, ensuring that all appropriate controls for family-wise error rate are taken.

Step 4: Write the report

Write a concise report containing an Introduction, Method, Results, and Discussion. Write it as if for publication in an APA journal – it should read like a polished and published piece of research rather than a statistics assignment. If you wish, you can include references (real or fake) and a reference list, but this is not necessary and will not be assessed. Reports will be evaluated based on specific criteria on the following page.

Guidance for preparing each section of the report:

Introduction (about 300 words, worth 15% of report)

Provide sufficient background to enable the reader to understand the logic and rationale of the design, but no more than this. Do not just give the outline of the design without a rationale.
State the research hypotheses. Do not merely do this in point form, nor give the null hypothesis for each effect. It is not enough to say that an effect of X was expected. Remember that using null hypothesis significance testing, it is not appropriate to hypothesise “no difference” or “no interaction”.
Your hypotheses must make sense as planned contrasts, i.e., they would be reasonable contrasts given your background “theory” and design.
Studies that include two classification variables, or that are not between-subjects designs (e.g., mixed or within-subjects designs), will incur a 10-mark penalty.

Method (about 200 words, worth 15% of report)

Subheadings such as Participants, Materials, Procedure may be relevant, depending on your design.
You must say how the independent variables were operationalised. It is not enough to just say something like “intervention”. You need to state how participants received this intervention.
You must clearly specify what the dependent variable is and how it was assessed. This should include what high/low scores mean. You are free to invent scales/measures if you want to. Your choice of dependent variable must be plausible given that it has a range of 0-50.

Results (about 200 words, worth 50% of report)

Do not report the results of the omnibus F tests.
Do not test simple effects and do not interpret interactions as if they were simple effects.
Specify your method of controlling FER, giving relevant critical F values.
Include complete verbal reporting of all results, not just tables of numbers (even non-significant results – e.g., it is not sufficient to say ‘the interaction between X and Y was not significant). The direction of differences must be specified for contrasts that are statistically significant.
Include a summary table of your planned contrasts results (you do not need a table of the contrast coefficients).
For each effect, compute and report a measure of effect size (partial eta-squared) – do not comment on this value, you just need to report it.
Include an appropriately-formatted table of the descriptive statistics for the dependent variable (for each level of the independent variable).
Make sure tables are formatted appropriately – do not just copy and paste from the SPSS output.
Include an appropriately-formatted graph of the data, with error bars and a sufficiently detailed figure legend.
Only information relevant to a Results section should be included. Inclusion of information inappropriate for a Results section will be penalised.
Unnecessarily verbose reporting of results or redundancy will be penalised.

Discussion (about 300 words, worth 20% of report)

Do not just restate the results, but interpret them with reference to their specific rationale. Interpret the overall findings together as a whole.
Note (meaningful) limitations of the study as well as (meaningful) possible future directions. Look at published research articles to see how it is done.

Appendix

Include the SPSS syntax that you have used as the last page of your assignment. This appendix must provide all the syntax that is required to replicate your ANOVA and contrast analyses.