44221: Information Systems Intro to Spreadsheets By:Ian Perry Room: C48 Tel:

Ian PerrySlide : Information Systems: Introduction to Spreadsheets When to use a Spreadsheet? Whenever NUMERICAL data requires: Calculation which may be complex, repetitive, or both. Presentation in tabular and/or graphical format. Analysis of complex situations. Exploration of probable outcomes.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets A ‘typical’ Spreadsheet ABCD R&D Cost Rent Travel Personnel TOTAL Columns Rows Text B6: Cell Reference =SUM(B3:B5) Formula Range Cell Numbers

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Data can be presented as a Chart A B C D E 1 1st Qtr 2nd Qtr 3rd Qtr 4th Qtr 2 East West North st Qtr2nd Qtr3rd Qtr4th Qtr East West North Which may make it easier to see trends, or spot exceptional/unusual values.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets The ‘simplest’ Spreadsheet Formula? Is a reference to another cell. NB. all formulae begin with an = sign. This is, perhaps, the MOST USEFUL spreadsheet formula; as, ideally, any data you wish to add to a spreadsheet should only be entered ONCE.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Simple Calculations i.e. using a Spreadsheet like a Calculator. NB. By default * and / happen before + and - So, be careful when/if using brackets in calculations, as: C6/D6+E6*(C6-D6) will produce a VERY different result, i.e.:

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Simple Spreadsheet Functions - 1 Sum =sum(range) OR =sum(cell, cell, …)

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Simple Spreadsheet Functions - 2 Average =average(range) OR =average(cell, cell, …) Try to avoid calculating averages like this: =(C14+D14+E14)/3 =(Sum(C14:E14))/3 as, if the number of data values in the range to be averaged changes, then you will have to remember to alter your formula.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Simple Spreadsheet Functions - 3 Standard Deviation (of population) =stdevp(range) OR =stdevp(cell, cell, …)

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Simple Spreadsheet Functions - 4 Maximum =max(range) OR = max(cell, cell, …) Minimum =min(range) OR = min(cell, cell, …) Median =median(range) OR = median(cell, cell, …) Count (of cells containing numeric data) =count(range) OR = count(cell, cell, …) Now (i.e. today’s Date & Time) =now() Today (i.e. just today’s Date) =today()

Ian PerrySlide : Information Systems: Introduction to Spreadsheets The ‘CountIf’ Function Counts the number of values in a range that match a given criteria. =countif(range,criteria)

Ian PerrySlide : Information Systems: Introduction to Spreadsheets The ‘IF’ Function Tests a condition in another cell, and decides what to display in this one. =if(condition,true,false)

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Nested ‘IF’ Functions To test for more than one condition, you could use a series of nested IF’s: =if(condition1,true,if(condition2,true,false))

Ian PerrySlide : Information Systems: Introduction to Spreadsheets The ‘VLookUp’ Function Much easier to use than nested IF’s, when there are many conditions to test for: =vlookup(value,range,offset) NB. the first column of the lookup table (i.e. column E in this example) MUST contain single data values AND be in Ascending order. Either: ALPHABETICALLY Or: NUMERICALLY

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Spreadsheet Development - 1 Draft it out on paper first, considering: Shape does the problem suit a landscape or a portrait shaped solution? Content which parts of the spreadsheet content will be text, data, formulae? Outputs will the data be presented in tabular and/or graphical format? is there a need to print the results or will they be viewed on screen?

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Spreadsheet Development - 2 Two types of data in a spreadsheet: Input data - entered/altered often, e.g. sales made, hours worked, money to change, etc. Reference data - rarely changes, e.g. vat rates, pay rates, currency conversion rates, etc. Always separate these data types: Keep input data areas together (and easily accessible) data entry is the biggest source of errors. Keep reference data together and protect cells where data entry is not required.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Spreadsheet Development – 3 Start simply: Do not try to build a large complex spreadsheet model containing features/functions you have never used before. Try out any new features/functions you want to use, by building a small controlled example. Test each stage in the development of your spreadsheet model: testing each new feature/function you add; gradually incorporating all of the functionality required. Don't get too clever, too soon!

Ian PerrySlide : Information Systems: Introduction to Spreadsheets Spreadsheet Development - 4 Save a "Template" i.e. a complete spreadsheet model without input data; containing text, formulae and reference data only. use a copy of this "Template" for testing. Test Rigorously use data which will produce known outputs; e.g. 1,1,1, or 50,50,50, or 100,100,100, sequences. use someone else to test ease of data entry; you may find your design is not as easy for others. Don't forget to amend the "Template"; if (when!) changes are required.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets This Week’s Workshop Complete this fairly simple spreadsheet model; by adding the missing formulae. These Lecture notes contain examples of all of the spreadsheet formulae you will need in order to complete the Workshop tasks. You MUST only enter ‘new’ formulae in the GREEN cells, then Copy & Paste to fill in the formulae for the remainder of each Column or Row.

Ian PerrySlide : Information Systems: Introduction to Spreadsheets The Completed Spreadsheet Model