Interviewing

Interviewing is one of the techniques that are used in Quantitative Risk Analysis. As mentioned in the previous chapter, it is part of the Data Gathering and Representation Techniques sub-group. 

At a high level, we all know what Interviewing is, isn’t it? But, in this chapter, we are going to learn what we need to know about interviewing from Quantitative Analysis perspective. What information we are looking to get through interviewing and what we are supposed to do with that information are a couple of questions that will get answered in this chapter. 

Interviewing in general, is used to quantify the probability and impact that risks may have on our projects objectives. The information gathered during these interviews would be dependent on the type of probability distributions that we are looking to use. Typically, we will conduct such interviews with SME’s (Subject Matter Experts) to get their take on the risk and its impact. Don’t worry too much about probability distributions just yet. We will be covering it very soon. For now remember that the data we gather could vary based on the type of distribution we use. That should be sufficient to understand the forthcoming section. 

For commonly used distributions, we gather three point estimates through these interviews. The three point estimate is calculated using the PERT Formula. Are you wondering what PERT is? If you are someone who has not studied the PMBOK Guide fully yet, I strongly urge you to do that because, the PMI RMP Exam uses a lot of terms and concepts that are part of the standard Project Management Framework as per the PMBOK. Anyways, PERT stands for Program Evaluation and Review Technique. It is a technique used to estimate durations for activities. In my earlier series on PMP Certification I had covered it in great detail in the chapter titled Estimating Activity Duration. 

In short – As per the 3 point formula, we try to arrive at 3 different estimates: 
a. The Optimistic Estimate (O) 
b. The Most Likely Estimate & (ML) 
c. The Pessimistic Estimate (P)

The 3 point estimate is a weighted average of these 3 estimates and is usually more accurate. The formula is as follows: 

3 point estimate = (O + 4 * ML + P) / 6 

The range here between the optimistic and pessimistic numbers is the range of uncertainty for our estimate. The more the uncertainty, the greater the range. Remember, the chapter titled Managing Uncertainty? Uncertainty causes risks and the whole purpose of Risk Management is to keep this uncertainty to the minimum. 

Trivia: 

Whenever we calculate any numbers or values, we must always document how those values were derived, along with any assumptions or constraints that went into the calculation. 

Standard Deviation: 

The Standard Deviation (SD) is a measure of how far the actual estimate we have calculated is from the mean value. The formula to calculate SD is:

SD = P – O / 6 

Here again – P is the pessimistic and O is the optimistic estimate. 

An Example: 

Let us say, you are talking to an Engineer about construction of a brick wall. He is an expert and is going to give you his feedback during the interview. He feels that, the brick wall could be constructed in 10 days if everything goes smoothly but, if it rains then the construction may get extended to up to 20 days. He also feels that, the construction should be complete in around 15 days. 

So, as per this discussion: 

O = 10 days
P = 20 days and
ML = 14 days 

3 point estimate = (10 + 4 * 14 + 20) / 6 = 14.33 days 

SD = 20 – 10 / 6 = 1.667 days 

As per the 3 point estimate we can say that, the construction of the wall will be completed in 14.33 days while the standard deviation will be 1.667 days. The SD signifies the fact that the construction may get shortened or extended by this value based on the prevailing conditions. So, the work could complete 1.667 days prior to the planned 14.33 days or it could take 1.667 days more than the planned days. 

So, the expected construction duration will be 12.663 days to 16 days. 

Trivia:

All estimates provided must be justifiable. You can’t just take the word of the SME for the numbers. Ask them for justifications and note them down for future reference. 

In this chapter, we have covered a lot of items pertaining to interviewing, estimates etc. From the PMI RMP Exam perspective, you need to remember the following: 

1. Interviewing is a tool and technique that is part of the Perform Quantitative Analysis Process and a part of the Data Gathering & Representation Techniques sub-group
2. We use this technique to gather information using historical data (or SME’s) and help quantify the probability and impact of Risks on project objectives
3. Information gathered using this technique depends on the type of probability distributions used 
4. The 3 point estimate formula is: (O + 4 * ML + P) / 6
5. The Standard Deviation formula is: P – O / 6

Prev: Tools & Techniques Used in Quantitative Analysis - Introduction

Next: Introduction to Probability Distributions

Points to Remember: Project Time Management

Resources are people, equipment, locations, or anything else that you need in order to do all of the activities that you planned for. Every activity in your activity list needs to have resources assigned to it.

Bottom-Up Estimating is a technique that you may have used before without even knowing it! It means breaking down complex activities into pieces, and working out the resource assignments for each of those simpler pieces using the other four tools and techniques.

Almost all of the outputs of Estimate Activity Resources are immediately used as inputs for Estimate Activity Durations, which is where your estimates come from.

Three-Point Estimates are when you come up with three numbers: a realistic estimate that’s most likely to occur, an optimistic one that represents the best-case scenario, and a pessimistic one that represents the worst-case scenario. The final estimate is the average. There is a formula associated with how you get the final value, but for simplicity sakes, remember that it is an average of these 3 numbers.

The Formula is:

Expected Duration = (Optimistic Duration + 4 times Most Likely duration + Pessimistic Duration) ÷ 6

Why 6? you are going to find the average of 6 numbers and hence 6. How 6? 1 Optimistic + 1 Pessimistic + 4 Most likely which means 1 + 1 + 4 = 6

Develop Schedule brings everything you’ve done in the other time management processes like Sequence Activities, Estimate Activity Resources, Estimate Activity Durations etc into one final schedule. All of the outputs from the other time management processes are inputs to Develop Schedule.

The Critical Path is the string of activities that will delay the whole project if any one of them is delayed.

The float for any activity is the amount of time that it can slip before it causes your project to be delayed. You might also see the word “slack” – it’s the same thing.

Early start - Is the earliest time that an activity can start. An activity near the end of the path will only start early if all of the previous activities in the path also started early. If one of the previous activities in the path slips, that will push it out.

Early finish - Is the earliest time that an activity can finish. It’s the date that an activity will finish if all of the previous activities started early and none of them slipped.

When you find the early start and early finish for each task, you know exactly how much freedom you have to move the start dates for those activities around without causing problems.

Late start - Is the latest time that an activity can start. If an activity is on a path that’s much shorter than the critical path, then it can start very late without delaying the project – but those delays will add up quickly if other activities on its path also slip!

Late finish - Is the latest time that an activity can finish. If an activity is on a short path and all of the other activities on that path start
and finish early, then it can finish very late without causing the project to be late.

Figuring out the late start and late finish will help you see how much “play” you have in your schedule. An activity with a large late start or late finish means you have more options.

Calculating the early start (ES) of an activity isn’t hard. All you need to do is look at the early finish (EF) of the previous activity and add one. If there’s more than one predecessor, then you take the largest EF and add one.

It’s just as easy to calculate the late finish (LF). Look at the following activity, take its LS (late start), and subtract one. If there’s more than one following activity, use the one with the lowest LS.

The float for an activity is the amount that its duration can slip without causing the project to be delayed. The float for any activity on the critical path is zero.

Managing schedule change means keeping all of your schedule documents up to date. When your schedule changes, you need to take performance measurements so you can keep your stakeholders up to date.

Remember: Gantt charts — the bar charts you make with MS Project, are just one tool for scheduling. You may use them a lot in your day-to-day work, but they’re only one piece of time management. And remember, on the exam they’re called bar charts, not Gantt charts!

Any time you generate data about your project, you should add it to your organizational process assets so you can use it for future projects.


Points to Remember - Other Topics:

Introduction to Projects & Project Management
Relationship Between Knowledge Areas & Process Groups
Project Integration Management
Project Scope Management
Project Cost Management
Project Quality Management
Human Resource Management
Project Communication Management
Project Risk Management
Project Procurement Management
Ethics & Professional Responsibility