This series of articles will give you an overview of how to manage spreadsheet risk. These articles are written by Myles Arnott from Excel Audit
- Part 1: An Introduction to managing spreadsheet risk
- Part 2: How companies can manage their spreadsheet risk
- Part 3: Excel’s auditing functions
- Part 4: Using external software packages to manage your spreadsheet risk

In the first article in this series we highlighted the risks that poorly managed spreadsheet solutions can introduce to a business. In this article we will demonstrate how companies can manage this risk.
A formal governance framework
The first, and arguably most important step is to ensure that the senior management team buy into the need for a robust spreadsheet risk management framework, and that they define and effectively communicate their spreadsheet risk management policy.
Spreadsheets identified and catalogued
It is impossible to know the level of spreadsheet risk in an organization without first identifying and then risk assessing all of the spreadsheets. It is therefore necessary to create a catalog of all of the spreadsheets and then to gather the key information about each spreadsheet to enable a risk assessment to be carried out.
The two key factors for determining the spreadsheet risk are the probability of there being an error and the impact that that error could have.
Risk = Probability of an error X impact if an error were to occur
The probability of error is related to the complexity of the spreadsheet. Complexity attributes differ across companies but include:
- Spreadsheet size (Mbs)
- Spreadsheet design (hard coded numbers in formulae, poor model structuring etc)
- The number of users
- The use of complex formulae (particularly array formulae, nested formulae etc)
- The number of cells populated
- The number of internal and external links
- The use of VBA
The impact of the error is related to how critical the spreadsheet is within the business. Each company will have a slightly different definition of the impact levels of spreadsheets, but generally:
- A spreadsheet is low impact if it is not used as part of a critical business process and an error would not have a material impact on the business.
- A spreadsheet is medium impact if it contains confidential information and an error could have a material impact on the business.
- A spreadsheet is high impact if it contains highly confidential information and an error would have a significant impact on the business. Spreadsheets used within processes that fall under external regulation (such as Sarbanes-Oxley and Solvency II) are deemed to be of high impact.
Finally, the spreadsheets should be placed in order of risk. Those identified as business critical and high risk should be prioritized for detailed review and placed under control.
This is clearly an on-going process. As new spreadsheets are developed they will need to pass through the risk assessment process as defined by the company’s spreadsheet risk management policy. A periodic review should also be carried out to ensure that all spreadsheets have been correctly categorized.
A best practice standard
The company should define its own best practice spreadsheet development standard that is applied to spreadsheets deemed to be medium or high impact. The standard should clearly outline the standards and conventions to which a spreadsheet should be built. New developments can then be reviewed to ensure that they adhere to the standard.
We advocate the use of the Excel Best Practice Standard from the Spreadsheet Standards Review Board (‘SSRB’).
We also recommend that tailored schedules are added to the standard to reflect your specific design standards. For example this could be a specific color scheme, use of logo or the use of specific text within the header or footer (e.g. document security levels).
Testing
A fundamental, but often overlooked step in the Excel model development cycle is testing. All spreadsheets (but especially business critical spreadsheets) need to be first peer reviewed and then rigorously tested.
It helps to consider the steps that an IT department would take to ensure that something they deliver is correct. It will pass through stages of unit and system testing prior to quality assurance and finally user acceptance testing. So why should a spreadsheet being used for a critical process be any different?
The fact is that no matter how hard we try, humans make errors. The purpose of testing is to identify them and get them resolved before the model goes into the live environment.
Remember that in the first article we highlighted the fact that 94% of spreadsheets and 5% of all formulae within spreadsheets contain errors.
Here is Scott Adams’ view on spreadsheet testing in Dilbert
Training
All staff should be trained so that they have sufficient Excel knowledge for their role and to use the spreadsheets that they are responsible for. As part of the induction process all staff should also be taught the company’s best practice standard.
Whilst this sounds obvious, research has shown that few companies prioritize investment in spreadsheet training.
Documentation
A key risk with spreadsheets is that they are often built and used by one individual within a team (often referred to as a “key man dependency”). If this person is ill or leaves unexpectedly the other members are totally reliant on the documentation left behind. From experience this rarely exists.
Each spreadsheet that is used within a process should as a bare minimum have documentation stating:
- the purpose of the spreadsheet;
- how the spreadsheet fits within the process;
- the source of all inputs for the spreadsheet;
- all key assumptions and drivers;
- key calculations;
- distribution list for outputs.
Spreadsheets that are part of as critical business process should have detailed documentation. This should include a technical specification and user notes.
Security
All business critical and confidential spreadsheets should be subject to access control. Security controls can be implemented across three levels:
- Directory level: Only specific individuals have access to key directories
- File level: Confidential and critical spreadsheets should be password protected to restrict access
- Cell level: Non-input cells should be password protected
Change control, backups and archives
To minimize the risk of losing the current version of a spreadsheet and ensuring that the correct version is being used at all times, all business critical spreadsheets should be backed up, archived and subject to change control procedures.
So, in summary..,
the characteristics of a well-managed environment are:
- a formal governance framework, sponsored by the senior management team, is in place for all spreadsheet development;
- a catalog of spreadsheets is maintained and prioritized by risk profile;
- a best practice standard is applied to the development of all new spreadsheets;
- all new spreadsheets pass through a formal risk assessment, are peer reviewed and formally tested;
- staff are provided with sufficient training to carry out their roles;
- all spreadsheets and their associated processes are well documented;
- access to critical spreadsheets is subject to security controls;
- spreadsheets are subject to change control and are regularly backed up and archived.
What next?
In the next article we will look at the built in Excel functions that can help you to manage spreadsheet risk.
What about you?
How do you (or your company) manage spreadsheet risk? What best practices & guidelines you follow? Please share using comments.
Thank you Myles
Many thanks to Myles for writing this series. Your experience in this area is invaluable. If you enjoy this series, drop a note of thanks to Myles thru comments. You can also reach him at Excel Audit or his linkedin profile.












12 Responses to “29 Excel Formula Tips for all Occasions [and proof that PHD readers truly rock]”
Some great contributions here.
Gotta love the Friday 13th formula 😀
Great tips from you all! Thanks a lot for sharing! bsamson, particularly you helped me on a terribly annoying task. 🙂
(BTW, Chandoo, it's not exactly "Find if a range is normally distributed" what my suggestion does. It checks if two proportions are statistically different. I probably gave you a bad explanation on twitter, but it'd be probably better if you fix it here... 🙂 )
Great compilation Chandoo
For the "Clean your text before you lookup"
=VLOOKUP(CLEAN(TRIM(E20)),F5:G18,2,0)
I would like to share a method to convert a number-stored-as-text before you lookup:
=VLOOKUP(E20+0,F5:G18,2,0)
@Peder, yeah, I loved that formula
@Aires: Sorry, I misunderstood your formula. Corrected the heading now.
@John.. that is a cool tip.
Hey Chandoo,
That p-value formula is really great for a statistics person like me.
What a p-value essentially is, is the probability that the results obtained from a statistical test aren't valid. So for example, if my p value is .05, there's a 5% probability that my results are wrong.
You can play with this if you install the Data Analysis Toolpak (which will perform some statistical tests for you AND provide the P Value.)
Let's say for example I've got two weeks of data (separated into columns) with the number of hours worked per day. I want to find out if the total number of hours I worked in week two were really all the different than week one.
Week1 Week2
10 11
12 9
9 10
7 8
5 8
Go to Data > Data Analysis > T-Test Assuming Unequal Variances > OK
In the Variable 1 Box, select the range of data for week 1.
In the Variable 2 Box, select the range of data for week 2.
Check "Labels"
In the Alpha box, select a value (in percentage terms) for how tolerant you are of error.
.05 is the general standard; that is to say I am willing to accept a 95% level of confidence that my result is accuarate.
Select a range output.
Excel calculates a number of results: Average (mean) for each week's data, etc.
You'll notice however that there are two P Values; one-tail and two-tail. (one tail tests are for > or .05), the number of hours I worked in week two is statistically equivalent to the number of hours I worked in week one.
So here’s a way you might want to use this. You put up a new entry on your blog. You think it’s the best entry ever! So you pull your webstats for this week and compare it to last week. You gather data for each week on the length of time a visitor spends on your website. The question you’re trying to prove statistically is whether there’s an average increase in the amount of time spent on your website this week as compared to last week (as a result of your fancy new blog post). You can run the same statistical test I illustrated above to find out. Incidentally, it matters very little to the stat test whether the quantity of visitors differs or not.
Anyhow, the Data Analysis toolpack doesn't perform a lot of stat tests that folks like me would like to have access to. In those cases I have to either use different software, or write some very complicated mathematical formulas. Having this p-value formula makes my life a LOT easier!
Thanks!
Eric~
Fantastic stuf..One line explanation is cool.
Thanks to all the contributors
OS
Take FirstName, MI, LastName in access (you can fix it to work in excel) capitalize first letter of each and lowercase the rest and add ". " if MI exists then same for last name:
Full Name: Format(Left([FirstName],1),">") & Format(Right([FirstName]),Len([FirstName])-1),"") & ". ","") & Format(Left([LastName],1),">") & Format(Right([LastName],Len([LastName])-1),"<")
I teach excel, access, etc etc for a living and i have my access students build this formula one step at a time from the inside out to show how formulas can be made even if it looks complicated. Yes I know I could just do IsNull([MI]) and reverse the order in the Iif() function but the point here is to nest as many functions as possible one by one (also I illustrate how it will fail without the Not() as it is)
Extract the month from a date
The easiest formula for this is =MONTH(a1)
It will return a 1 for January, 2 for February etc.
if in a column we write the value of total person for eg. 10 if we spent 1.33 paise each person then how we get total amount in next column and the result will in round form plzzzzz solve my problem sir................... thank u
@Anjali
If the value 10 is in B2 and 1.33 paise is in C2 the formula in D2 could be =B2*C2
If the values are a column of values you can copy the formula down by copy/paste or drag the small black handle at the bottom right corner of cell D2
kindly share with me new forumulas.
How to convert a figure like 870.70 into 870 but 871.70 into 880 using excel formula ? Please help.