NV4602

RESEARCH METHODS FOR
POSTGRADUATE STUDY
Analysing Groups and Relationships

Aims for today
 Understand what statistical tests are and why use them
 Choose the right test for the data
 Identify the preparatory steps
 Examine relationships
 Calculate Pearson’s r on SPSS

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Research questions
 Researchers often want to know if there is a significant relationship between two variables
 Is there a relationship between waiting time and customer satisfaction?  Is there a relationship between TV ads and number of sales?
 Is there a relationship between employees’ levels of stress and customer defection?
 Does gender predict early technology adoption?

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Research questions
 Or if there is a difference between one or more scores/conditions/groups 
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Is product A more attractive than product B?
Does working in pairs improve performance?
Does working from home decrease productivity?
Has the new manufacturing process increased productivity?
Does gender affect the frequency and size of online purchases? navitas.com

Statistical tests: Why we need them?
 Does marital status affect life satisfaction?
 ‘In a scale from 1 to 8, how satisfied are you with your life?’
 Great! I found a difference!!

 How confident are you? Is it an accident (due to chance)?
 We need to have a statistical test! lbic.navitas.com navitas.com

Choosing the right test
 If you browse any introductory statistics text book you’ll find a bewildering array of different statistical tests
 Each has
 a specific purpose (i.e. exploring relationships, comparing groups)  Specific data requirements (categorical, ordinal or continuous data, normal distribution)

 SPSS makes it easy to run most of the well known tests
 However, it is important to be able to
 Select the most appropriate test given your research question
 Understand conceptually what the test is computing
 Effectively interpret the output (SPSS often gives more than one result per test) lbic.navitas.com navitas.com

Preparatory steps
1. Choose the right test depending on your research question
2. Select your variables
3. Describe your data

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Step 1: What is your question?
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Remember, when conducting research it is important to be clear about the questions you are trying to answer
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Ideally before you begin data collection

The questions...

 Is there a relationship between waiting time and customer satisfaction?  Is there a relationship between TV ads and number of sales?
 Is there a relationship between employees’ levels of stress and customer defection?
 Does gender predict early technology adoption?

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...require quite different statistical tests to questions like:
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Is product A more attractive than product B?
Does working in pairs improve performance?
Does working from home decrease productivity?
Has the new manufacturing process increased productivity?
Does gender affect the frequency and size of online purchases? navitas.com Tests of relationship vs. tests of difference
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Questions of the first kind are about relationships. Common techniques include:
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Correlation – are variable X and variable Y related?
 E.g. Head size and IQ, salary and job satisfaction

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Questions of the second kind are about differences between groups/categories: 
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Chi-square shows whether there is an association between two categorical variables (e.g. Is gender associated with smoking?)
T-tests measure the difference between two groups (e.g. males, females) according to some continuous variable (e.g. Height, sales, job satisfaction)
Analysis of variance (ANOVA) measure differences when there are more than two groups and/or more than two independent variables
(e.g. marital status as in slide 4)

Today we will look at Pearson’s r correlation

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Step 2: Select your data
 Which variables will you be