The table of means presents the average score
for each product and attribute in sensory analysis and each product and consumer
rating (liking, JAR or CATA) in consumer analysis. The means are averaged
across assessor, sessions and replicates. These means can be used to begin to
explore the data and understand how products differ.
For EyeOpenR to read your data, the first five
columns of the ‘Data’ sheet must be in the following order: assessor
(consumer), product, session, replicate and order (sequence). For sensory
analysis the data for attributes should be in the sixth column (column F)
onwards. There should be one column for each attribute. The attributes data
should be numeric. For consumer analysis the data for consumer liking and other
consumer assessments (ratings) should be in the sixth column (column F)
onwards. There should be one column for each rating. These are described as
attributes in the options.
If there is no session, replicate or order
information then these columns should contain the value ‘1’ in each cell.
Additional information about the data in the
‘Data’ sheet can be included in additional sheets. The ‘Attributes’ sheet can
be used to specify the names of the attributes, data types and minimum and
maximum values that are used to check data quality. The ‘Assessors’ sheet can
be used to specify assessor names if codes are used in the ‘Data’ sheet.
Similarly, the ‘Products’ sheet can be used to specify product names if codes
are used in the ‘Data’ sheet. See the example spreadsheet for an illustration
of the data format.
Background
It can be helpful when first looking at
sensory and consumer data to explore the means averaged across assessor,
sessions and replicates. This gets to the information that is of most interest,
ie how products differ from each other.
There is also the ability to look at this data
one assessor at a time, or one session at a time or one replicate at a time.
This can be useful to get a better understanding of the data.
This module does not test whether differences
between products are statistically significant. Use other modules such as ‘ANOVA
for multiple comparison tests’ to do this.
Options
- Split
results on: There are five options here; None, Judge,
Attribute, Product, Session. If a choice is made other than None, the results
are presented separately for each level of the split selected. For consumer
studies ‘Attribute’ refers to the consumer ratings. Note that if a split is
selected, and the Type of Mean selected is ‘Adjusted’ then EyeOpenR compares
the chosen model with the split option and if it is not possible to calculate
adjusted means this option will be ignored and a message written into the
‘Information’ tab of the results.
- Treat
Sessions/Replicates Separately: There are three options; ‘No’,
‘Sessions’, ‘Replicates’. Only one option can be selected. If either sessions
or replicates is selected then each results table shows results for each
attribute split by either session or replicate.
- Type
of Mean: There are two options: ‘Adjusted’ presents
adjusted means derived from an ANOVA specified using the four options that
follow. ‘Arithmetic’ presents unadjusted means and if selected the next four
options are greyed out because they are not needed. If the design of the study
is balanced then adjusted and arithmetic means are identical. If the model
selected is not compatible with choices made for the Split results by or Treat
Sessions/Replicates Separately options then the arithmetic means are calculated
and note is written to the ‘Information’ tab of the results.
- Assessor
Effect: Only available if ‘Adjusted’ means have been
selected. Includes assessor effects in the ANOVA and therefore means are
adjusted for assessor differences.
- Session
Effect: Only available if ‘Adjusted’ means have been
selected. Includes session effects in the ANOVA and therefore means are
adjusted for assessor differences.
- Replicate
Effect: Only available if ‘Adjusted’ means have been
selected. Includes replicate effects in the ANOVA and therefore means are
adjusted for assessor differences.
- Interaction:
Only available if ‘Adjusted’ means have been selected. If at least one of the
preceding three effects has been selected, the two-way interaction of product
and those effects is also included in the ANOVA. If no other effect has been
selected, the ANOVA is a 1 way ANOVA with product and this option is ignored.
- Number
of Decimals for Values: Specify the number of decimal places
shown for means.
Results and Interpretation
- Means:
This shows a table with products in the columns and attributes in
the rows. The table includes the means (or adjusted means depending on the
option selected for the ‘Type of Mean’). If the ‘Split results on’ option was
anything other than ‘None’ there is a table for each of the split levels. These
are selected at the very top of the page. If the ‘Treat Sessions/Replicates
Separately’ option has been selected then each table has additional rows, one for each level of attribute and either
session or replicate. The more granular the data the fewer the number of
observations in the means. The tables are presented with the products in the
columns so that you can compare products for each attribute by looking at the
values in each row.
- Information:
This shows any notes or warnings that are relevant to the
procedure. If the adjusted means have been selected a description of the ANOVA
model is included here.
R packages used:
- averagetable (SensoMineR) for
calculating the means.
Reference
- Martin Bland (2015)
“An Introduction to Medical Statistics – 4th Edition”, Oxford University
Press. See chapter 4 “Summarizing data”.