Chapter 4

Chapter 4

1. Mathematical modelling

   • Spreadsheets
     • Columns and rows in an easy to follow format
     • Used for financial modelling
     • Rows and columns allow the user to use replication and sequencing
   • Variable & constants
     • Variable is a changeable value which is entered into a cell and used in a formulae
       • Currency conversion will be a variable
         • The user can change the amount converted
     • Constants are values that cannot be changed by the user
   • Cell names
     • This would also make formulae easier to understand
     • The user may give a cell a name relating to its contents
       • E.g. C10 could be VAT_RATE
   • What-if
     • The user can adjust the values and see how the numbers react
     • Or start with the results and see what needs to happen in order to get that value

2. Why is computer modelling used?

   • Only one model needs to be created
     • If the real model was created, the the whole model would have to be built for alteration
     • Model can be altered & changed
   • Can be accelerated or slowed down
     • In order to see effects
     • E.g. The creation of Earth was a long process and can be sped up
     • E.g. An explosion can be slowed down
   • Less risky
     • Safer & cheaper
     • E.g. To test a aircraft as in real life it could risk lives
     • You can test a model before it is created
   • Can be backed up & shared
     • Can be backed up on a disk
     • Can be emailed

3. WHAT-IF?

   • Attempt to find out what is going to happen in the future
   • A what-if question needs the question and what could be changed
   • Benefits
     • Recalculation: values can be changed multiple times and values will adapt to the changes made
     • Less time & cost: quicker and cheaper than creating the actual model
     • Errors: If there is an error it is quicker and easier to alter it rather than on a physical model

4. Advantages of using a spreadsheet to create and run models

   • What if questions can be asked without rebuilding the model, each time a test is run
   • Automatic recalculation
   • Variables and constants
   • Models can be backed up and shared

5. Disadvantages of using a spreadsheet to create and run models

   • The model cannot be an accurate representation of the real world
   • Many variables may need to be considered so it would be easy to miss things out, which may lead to misleading results
   • Producing a model can be time consuming and running the model may need expensive hardware and software

6. Describe and explain...

   • Worksheet: is a large grid of cells on a single sheet. A worksheet can be used to hold data on a single area of a business
   • Workbook: A collection of more than on worksheet in the same spreadsheet
   • Cell: An individual data store identified by a row and column indicator, every cell is uniquely identified
   • Rows& columns: Rows are a range of cells that go across the spreadsheet, a column is range of cells that go down the spreasheet
   • Range: is a group of cells, a group can be given a name or just known by their cell references

7. RELATIVE AND ABSOLUTE REFERNCING

   • Relative referencing- when the cell in a spreadsheet formula changes when the formula is copied
   • Absolute referencing:when the referenced cell needs to remain the same when the cells are copied to other cells