Check sheet

Check sheet
One of the Seven Basic Tools of Quality
Purpose	To provide a structured way to collect quality-related data as a rough means for assessing a process or as an input to other analyses

The check sheet is a form (document) used to collect data in real time at the location where the data is generated. The data it captures can be quantitative or qualitative. When the information is quantitative, the check sheet is sometimes called a tally sheet.

The check sheet is one of the so-called Seven Basic Tools of Quality Control.

The defining characteristic of a check sheet is that data are recorded by making marks ("checks") on it. A typical check sheet is divided into regions, and marks made in different regions have different significance. Data are read by observing the location and number of marks on the sheet.

Check sheets typically employ a heading that answers the Five Ws:

Kaoru Ishikawa identified five uses for check sheets in quality control:

When assessing the probability distribution of a process one can record all process data and then wait to construct a frequency distribution at a later time. However, a check sheet can be used to construct the frequency distribution as the process is being observed.

This type of check sheet consists of the following:

Note that the extremes in process observations must be accurately predicted in advance of constructing the check sheet.

When the process distribution is ready to be assessed, the assessor fills out the check sheet's heading and actively observes the process. Each time the process generates an output, he or she measures (or otherwise assesses) the output, determines the bin in which the measurement falls, and adds to that bin's check marks.

When the observation period has concluded, the assessor should examine it as follows:

If there is evidence of non-normality or if the process is producing significant output near or beyond the specification limits, a process improvement effort to remove special-cause variation should be undertaken.

When a process has been identified as a candidate for improvement, it's important to know what types of defects occur in its outputs and their relative frequencies. This information serves as a guide for investigating and removing the sources of defects, starting with the most frequently occurring.

This type of check sheet consists of the following:

Note that the defect categories and how process outputs are to be placed into these categories must be agreed to and spelled out in advance of constructing the check sheet. Additionally, rules for recording the presence of defects of different types when observed for the same process output must be set down.

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