Sampling Basics

There are certain vital techniques which must be understood well if we want to understand the subject of statistics and measurements. Sampling is one such very important topic, which we’ll be covering in a couple of articles.

Some terminologies first…

To understand the concept, we should also understand a few frequent terms.

• Element– an object on which a measurement is taken
• Population– a collection of elements about which we wish to make an inference
• Sampling units non-overlapping collections of elements from the population that cover the entire population
• Sampling frame– a list of sampling units
• Sample- a collection of sampling units drawn from a sampling frame
• Parameter: numerical characteristic of a population
• Statistic: numerical characteristic of a sample

What is Sampling?

The activity in which elements, from a population, are collected so as to represent the population. In this video, a very good introduction to sampling has been provided.

Why Sampling?

Most of the times, the population is too large to measure all of its elements, thus sampling is done. A sample reflects the characteristics of the population from which it is drawn. For example, a machine produces 1000 spindles a day. It may be difficult to measure all of them, so we take samples and measure them.

It is very crucial that samples are selected carefully. Incorrect sampling may lead to incorrect inferences about the population.

Sampling has many advantages over exhaustive sampling, which covers the whole population.

• Sampling can save money
• Sampling can save time
• In case of destructive inspection, it is not prudent to do exhaustive sampling

In our next article, we’ll learn about the common sampling techniques.

Learn all about sampling techniques along with statistical techniques in our upcoming training on Lean Six Sigma (green belt). Enroll for the training now and get a 20% discount when you pay.

Our free basic training available-

The three D’evils!

What is it that comes as the biggest challenge in the way of an organisation towards success?

There are, and can be, an infinite number of reasons. But the three D’s, or the three Devils, look to pose a serious threat for an organisation to succeed.

1. Defects:

When the effort and money go in fixing things which should have been done ‘right first time’, it is definitely going to cost an organization way more than it can assess! With every defect in the delivered item, it is losing the faith of the customer and it is needless to mention that eventually, it’ll lose the business.

Even, if an item is not delivered yet, then also the employees are on fixing spree, which is consuming time as well as money that could be better spent serving customers and strengthening the bottom line.

2. Delays:

Just like defects impact business, delays are also not taken positively by the customers. Delays between the process steps cost time and money and can negatively impact  the productivity and profitability.

Within the organisation, delays may lead to frustration of the employees and when the delivery is impacted, it may frustrate the customer as well.

3. Deviation

When the product or services have small to the large difference in the output, the confidence of meeting customer specifications/ needs goes down.

Think of the scenario where you are going to tighten a nut…but the bolt is not of the right size. It is going to stop your work. There are parts which are just right, while sometimes we get some parts which are too big or too small to be used.

Deviations are the unwanted difference in the output of the same process. Some amount of deviation is inherent and can be lived with…but when the deviation is beyond certain agreed limits, called the specification limits, it starts causing the problem.

So, any organization, irrespective of their industry, must be cautious of the three Devils and always work in the direction to keep these away.

Lean Six Sigma- pointers that you need it!

If you see one or more of the following symptoms, Lean six sigma is definitely the prescription…

Trying too hard still the customer is unhappy with the quality of your service or product? Lean six sigma methodology comes to your rescue here. Though the subject is vast but since it is a proven, data-driven, problem-solving methodology, you can definitely look into its prospects.

Roadblocks! Try Lean! It talks about improving efficiency and removing waste. Removing wastes from the process flow and adding value lie in the core of lean philosophy. All you need to do is instil Lean principle into your organisation’s culture.

Customers are returning products for refunds

Now this is a direct indication you must go Lean-Six-sigma! Where Lean helps in increasing efficiency (improving time to serve to the customer), Six sigma  helps in increasing effectiveness (improving the quality of the service/ product).

Warranty costs are climbing

Not able to fulfil the promises you’ve made about quality and reliability of your product? Or, is the cost of post delivery maintenance and product returns making a big hole in the revenue generated? Lean six sigma can help you in establishing/ fine-tuning your processes which will generate way better quality products.

Customers are switching to your competitors

This hurts a lot! And, you would want to do anything in your capacity to retain your customers. Work on increasing efficiency and reducing defects, show the value that you provide to the customer. Adopt Lean six sigma and show your customers that you are giving them the best-in-class products/services.

Margins are going down