1. C. Demetriou (2009) November 1, 2009 1
ž Modelling of objects
ž Modelling of Data
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2. ž Allows you to create virtual
representations of objects
such as :-
› Buildings
› Cars
ž You can look at the effect
of outside influences.
› Impact
› Earthquakes
› Fire
› Explosions
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ž Possible to see different layers
› Internal View
› External View
› Wireframe
› Electrical systems
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3. ž The ability to ask questions of the model.
ž Changing components to see the effect
or how it reacts.
ž Effects can be gauged at the touch of a
button.
ž Without having the risk of building the
real thing.
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ž Mathematical modelling
ž Predictions in Finance
› Using spreadsheets
› Allows replication of values
› Allows sequences to be setup
› Allows What If Scenarios to be modelled
C. Demetriou (2009) Nov ember 1, 2009 6

4. ž What features make
spreadsheets ideal for
modelling?
› Functions
› Formulae
› Variables
› Automated calculations
(refreshed)
› Great for trying out different
scenarios
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ž Variables
› An identifier associated with a value stored in
the model. The value may be in a cell or in
memory
ž Formulae
› Formulae allow calculations to be represented in
a spreadsheet. As well as numbers, a formula
uses the addresses of cells to identify other
values to be used. The result is placed in the cell
in which the formula was placed
› If any of the cells used on the formula change
their value, the result of the formula is updated
– E.g (I2-2*B3)/2
C. Demetriou (2009) Nov ember 1, 2009 8

5. ž These are special types of formulae used in a
spreadsheet
ž They are used to represent formulae that may
be too large or complex for the ordinary user to
enter:
› SUM() – to add a range of numbers
› AVERAGE() – to calculate the average of a range
› HLOOKUP() – to find one value based on another in a
horizontal list
› VLOOKUP() – to return a value based on another in a
vertical list
› IF() – to make a decision based on a value and
give an answer whether its TRUE or FALSE
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ž Rules are a set of procedures that must be
followed. For example, if a calculation
requires two values, then these values must
be supplied.
ž Validation rules ensure that data entered
meets a criteria or is present.
ž Could be coding:-
For each cadidate
For each module
Enter a UMS mark
Add all the marks together
Lookup the mark in the grade table
Return a grade
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6. ž Answering ‘what-if?’ questions
› A model can recalculate values – this allows
single values to be changed and the rest of
the model to be updated automatically
› Various combinations can be tried with
minimal effort
› ‘What if’ questions are predictive by nature
ž Advantages of using a data model
for ‘What if?’ questions:
› Only one model needs to be created and
then altered
› Many different possibilities can be tried -
repeatability
› Mistakes can be eradicated prior to
construction
› Cost of creating a changeable model against
several different models
› Safety of the model – nuclear explosion, trip to
Mars. Virtual Vs Physical models.
› Control over the variables
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ž Drawbacks of using spreadsheets to
create or run a spreadsheet
› Model may not be an accurate
representation of the real world.
› If the model relates to people then an
accurate result may not be given.
› Many Variables need to be considered
and it is easy to miss things out.
› Producing effective models can take a
lot of time and may need expensive
hardware and software.
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7. ž Worksheets and Workbooks
› A number of worksheets within a single file is called a workbook. A
workbook can be used to divide information between different
sheets, for example income on one sheet, expenditure on another,
and a summary on a third
ž Rows
› Rows are a horizontal group of cells. In Excel they are identified by
Number
ž Columns
› Columns are a vertical groups of cells. In Excel they are identified by
Letter
ž Cells
› A cell is the square on a spreadsheet in which only a single entry
can be placed. The entry can be text, numbers or a formula. It can
be referred to by its address based on its row and column
ž Ranges
› A range is a group of cells – usually identified by the address of the
top left cell to the bottom right cell: A1:G5 for example
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ž Replication is the process of copying a formula from
one cell to another
› As a formula usually involves references to cells, it is
necessary to know whether you want to keep the
references the same (absolute reference) or change
according to the row or column movement (relative
reference)
ž An absolute reference always refers to the same cell.
Anchors are created using $ sign eg. $A$3. Anchors
are needed on either Rows or Columns.
ž A relative reference changes the cell it references
according to the movement of the target cell. There
are no anchors on relative references such as A3
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8. A B C D The formula in Cells
C2:C4 is replicated
using both relative and
1 Good Price VAT Payable VAT
absolute replication.
2 Pen £50 =B2*$D$2 17.5% When the cell is
replicated down, the
reference to B2 needs
3 Watch £200 =B3*$D$2 to change so that the
price changes.
4 Ring £500 =B4*$D$2
However, the reference to cell D2 cannot change. If it was to
change to cell D3 the formula would not work, as there is
nothing in cell D3. Therefore as C2 is replicated, the reference to
B2 needs to change, hence it is a relative reference, but the
reference to D2 must not change, so it is absolute.
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ž Form Controls
› They include items like:
– Spinners
– Drop down boxes
– Buttons
› They are used to increase the usability of the
spreadsheet – list/drop down boxes can limit
data entry, making validation easier!
› Buttons can run Macros
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