The Seven Basic Tools of Quality are a collection of relatively simple graphical techniques that are often used to determine the root causes of errors and to help understand variation in process performance, all with an eye towards improving quality. It turns out that a great many problems can be understood by using only these tools.

Unlike more advanced methods such as sampling, DoE (design of experiments), hypothesis testing, multivariate analysis and some aspects of Operations Research that require a solid understanding of statistics and other advanced mathematical techniques, the seven tools are simple and graphical in nature. It is commonly believed that they were introduced sometime after 1960 to Japanese manufacturing by Kaoru Ishikawa who in turn was probably influenced by W. Edwards Deming.

The seven tools are:

• Cause-and-effect diagram (this is often called an Ishikawa or "fishbone" diagram):
• This is frequently used to research the root cause of a problem. It is usually drawn as a horizontal line with three to four diagonal lines coming off the horizontal line both above and below. Each of the diagonal lines corresponds to a common cause of problems such as "People", "Equipment", "Process", "Materials", etc. Then a process of asking "Why" is started and as each cause of the problem is identified, additional lines are added to the diagonal lines representing an increasingly detailed explanation for the problem. The resulting diagram can look like the "bones of a fish".
• Check Sheet:
• This is a simple form that is specifically designed to make it very quick and easy to enter information. In fact, is is usually designed to use checkmarks rather than entering data, hence the name. A Check Sheet is often used to ensure that a process is followed as designed or to record tallys of observed items.
• Control Chart:
• It is reasonable to think of a Control Chart as a Run Chart (below) with information, usually in the form of horizontal lines, added to indicate the "span" of variability in the process output. There are a variety of recommended ways to sample the process output to be plotted based on the type of process.
• Histogram:
• This is a common "bar-chart" type of graph that is used to record the frequency of events that fall into a set of categories. Once created, it is easy to see the relative frequency of occurrence of the various events.
• Pareto Chart:
• This chart can be thought of as a Histogram with a line graph above the bars showing the accumulated values of the bars in the Histogram. The Histogram bars are arranged from largest to smallest and the line graph is an increasing graph that shows how much each Histogram category is contributing to the total. This is the classic "80% of something is caused by only 20% of something else" chart.
• Run Chart (this is sometimes called a Stratification Chart):
• This is a line graph that records the output of a process over time. It is helpful in discovering patterns and trends in process output.
• Scatter Diagram:
• A Scatter Diagram is used to search for possible correlation between two items of interest. Pairs of observations are made and the resulting data pairs are plotted on an X-Y graph. If the plotted data points suggest a line or curve or other pattern this is considered suggestive of a correlation between the two items. If the resulting diagram just appears to have data points randomly "scattered" about, then the chance of a correlation is much lower.