Summary of the course Marketing Research Methods, in 2017 by Maarten Gijsenberg. Summary contains info of all slides and all comments given by Maarten Gijsenberg.
How do customers think about our product?
What are aspects that are good?
➢ Often, one-item scales:
o Do you like the taste of this brand?
o How old are you?
But, marketing concepts are more often too complicated for one item scales
So: multi item scales
- Attitudes
- Lifestyles
Another but: multi-item scales often have too many items for further analysis
➢ Reduce data again
o So, data reduction
▪ Factor analysis
▪ Reliability analysis
SCALES
➢ How to develop multi-item scales?
o Multi-stage process
Data analysis often in 2 stages
➢ Stage 1: inspection and preparing data for final analysis
o Inspection of data (items)
▪ Which variables / measurement scales / coding scheme
• Get a feeling for the data
▪ Cleaning your dataset
• Oddities, missing/wrong values, outliers…
o Age 165? Probably not right
o Missing age?
• Combining items into new dimensions
o E.g. factor / reliability
➢ Stage 2: Finally analysis, testing your hypotheses
, o E.g. regression analysis using the new dimensions instead of original items
Crap in = crap out if your data is crap, your outcome will be crap.
FACTOR ANALYSIS
➢ Purpose:
o Reduction of a large quantity of data by finding common variance to
▪ Retrieve underlying dimensions in your dataset, or
▪ Test if the hypothesized dimensions also exist in you dataset.
➢ Two central questions
o How to reduce a large(r) set of variables into a smaller set of uncorrelated factors?
▪ Unknown number and structure
▪ Hypothesized number and structure
o How to interpret these factors (= underlying dimensions), and scores on these
factors?
➢ On exam; technically rights means 50% of the points, use granny check. Say in easy language
what it means
Factor analysis: what is it about?
➢ Ultimate goal
o Use dimensions in further analysis
▪ E.g. position brands on these dimensions (with the supermarkets example;
price versus service)
▪ E.g. relationship export performance and attitude entrepreneur (regression)
➢ Data
o Interval or ratio scaled variables
▪ Likert scales; 1-5 or 1-7 for example
▪ Often ordinal, but assumed interval (likert)
➢ Note:
o No distinction is made between dependent (Y) and independent (X) variables!
▪ But: FA is usually applied to your independent variables (X)
▪ No causal relation between the variables
➢ Data reduction
o Metrical data on N items
o Summarize the items into p < n ‘factors’
▪ Hence; data reduction
o Two ways to do so
▪ Factor analysis
• Newer technique
• Mostly used for multi-item scales
• ‘Absolute’ method
• Covered in this course
▪ Multidimensional scaling
• Older technique
• Often used for positioning research
• ‘relative method’
• Not covered here
➢ Why can we reduce the number of variables?
, o If multiple things look the same, why not including a combination instead of
including all of them separately?
➢ Strong correlations between two or more items
o Same underlying phenomenon
o So combine, to get
▪ Parsimony (explaining a lot by little)
▪ Less multicollinearity in subsequent analysis (regression analysis)
• If variables are highly correlated, it’s hard to distinguish their effects
in regression
Just a first check, very rough, gives you an idea what might work in the end to combine variables in 1
and the same factor.
Basic concept
➢ Suppose we have X1, X2, X3, X4, X5, X6
➢ Any set of variables X1… X6 can be expressed as a linear combination of other variables, called
factors F1, F2, F3, F4, F5, F6 based on common variance in X1… X6
➢ You choose only the ‘strongest factors’
o Best number of factors unknown upfront
o E.g. 2 factors F1 & F2
o You try to explain as much as possible of X in as few as possible F’s
➢ Will never be done perfectly, info gets lost
o E.g. F3, F4, F5 and F6 are not being used.
➢ All variables load more (thick arrow) or less (thin arrow) on all factor
, ➢ We are looking for high-loading items
o We are interested in high loading (marker items) to label the dimensions (loading >
.5)
▪ The other lines are still ‘there’
➢
➢ Dimensions
o From now on, we only work with the dimensions = combinations of the original
items.
o The dimensions retrieved are now uncorrelated with each other
➢ Summarizing
o From n (way larger) >> m items
o Which items?
o Suitable items?
o How many dimensions?
o Suitable dimensions?
o Content / label dimensions?
➢ Important:
o Items = variables = survey questions
o Dimensions = factors = components
➢ STEPS for FA using SPSS
Step 1 Research purpose
▪ Which variables? How many? Sample size?
Step 2 Is FA appropriate?
▪ KMO measure of sampling adequacy
• Sampling adequacy predicts if data are likely to factor well, based
correlation
• If KMO < .5, drop variable with lowest individual KMO statistics
• Bartlett’s test of sphericity
o H0: variables are uncorrelated, i.e. the identity matrix
o If we cannot reject H0, no correlations can be established
o We need correlation among the variables, we need to reject
the H0 of uncorrelated variables.
• NOTE: also check the communalities
o Common rule: > .4
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