Histograma+pareto v375r

HISTOGRAMA

The histogram is used when we want to work with a big set of data, which we want to organize in an easy interpret manner. A histogram will show us where the majority of values are on a scale and how much variation exists. Also, the data processing results for a histogram created in Excel can show us if a process is between the interval’s limits where the variation is considered normal.

Analyzing the 4 possible situations presented in figure 1, we can it the following things about the described processes: 

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Histogram from figure 1, point A represents a stable process (because the data don’t vary too much and are not very spread) and capable (because most of the values – the highest column – fall exactly on the target – target process, what must result from it; example: a production process that must realize on average 20 products per day) Point B, represents an unstable process (we can observe a bigger data spread in comparison with point A), and still capable (most of the data fall also on the target) Point C, represents an incapable process (the data gather on the left side of the target), but stable (the data aren’t very spread)

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Point D represents an incapable process (data are gathered far from the target) and unstable (there is a big data spread).

DIAGRAMA PARETO

Pareto principle shows us that there are many situations where 80% of the consequences are provoked by 20% of causes. Vilfredo Pareto, French economist, discovered that in Italy (in 19th century) 80% of the properties were owned by only 20% of population. After that, Joseph Juran (Romanian immigrated in America) introduced the principle in managerial theories also. Pareto

law can be frequently seen, under different forms, in the management of many businesses’ type, for example:      

80% of incomes are generated by 20%of clients 80% of a project’s activities are realized in the 20% of the time assigned to the project 80% of wastes are caused by the 20% of production errors 80% from the inventory’s value is owned by only 20% of the storage space 80% from a magazine’s news stay in the 20% of the magazine’s space 80% of decisions are taken in the 20% of the time assigned for the meeting.

Of course that we don’t have to understand these references in absolute numbers. The main idea is that “the majority of the results are due to a reduced set, but very important, of resources” – the other way around being also valid. Aplicație: Application:

Ace Printing Company observed that they started losing clients and orders because of different delays and errors. In order for them to discover the main cause, they have decided to study the

problems that contribute to clients’ low level of satisfaction. The next list with the identified problems shows their frequency on a 6 month cycle. The company aims to allocate resources only for solving those problems that cause the majority of defects. To identify these problems, we will use a Pareto chart.