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- Six Sigma Tutorial
- Six Sigma DMAIC process
- Six Sigma Acceptance Sampling
- Sampling Plan Variation vs Lot Size Variation in Acceptance Sampling
- AQL Based Sampling Plans
- Decision Tree for Selecting Type of Variables in Sampling Plan
- FMEA – Failure Mode and Effects Analysis
- Types Of FMEA: Design FMEA (DFMEA), Process FMEA (PFMEA)
- The FMEA Quality Lever – Where To Put The Effort
- FMEA Quiz
- Six Sigma Confidence Intervals
- Confidence Limits
- Confidence Interval Formulas
- Z Confidence Interval for Means – Example
- t Confidence Interval for a Variance – Example
- Six Sigma Defect Metrics – DPO, DPMO, PPM, DPU Conversion table
- Fishbone Diagram – Fishbone Analysis
- Cost of Quality Defects and Hidden Factory in Six Sigma
- Pareto Analysis using Pareto Chart
- Six Sigma Calculators – DPMO, DPM, Sample Size
- How to select a Six Sigma project? Download selection grid template.
- How to create Six Sigma Histogram? Download Excel template
- Scatter Plots – Free Six Sigma Scatter Plot template
- How to create, use Six Sigma SIPOC tool? Download SIPOC Template
- Quality Function Deployment (QFD) – Download free templates
- What is Decision Matrix or Decision Making Matrix ?
- The nature of Process Variation
- What is RACI or RASCI Matrix/Chart/Diagram? Download free templates

A scatter diagram is a graphical representation of two variables, one on X axis and the other on Y axis. Hence they are also known as XY plots. A Scatter plot depicts the relationship between the two variables and determines if there is a correlation between those two variables.When one variable changes if the other variable changes, then a correlation is said to exist between those two variables. We can use the correlation to predict behavior. Its very useful if one variable is easy to measure and the other variable is difficult to measure.

Scatter plots show large amounts of data in a chart form. When the points on the scatter plot come closer making it a straight line, the correlation between the variables is higher and the relationship between the variables is stronger.

Correlation Coefficient is measured as:

R = [N * Sum(XY) – Sum(X)*Sum(Y)] / SQRT [N * Sum (X^2) – (Sum(X))^2] * SQRT [N * Sum (Y^2) – (Sum(Y))^2]

R is always between -1 and +1

Coefficient of determination is the square of R or R squared. This is always a positive number between 0 and +1

If the straight line goes up from left to right with **higher **values of X corresponding to **higher **values of Y then the correlation is said to be positive. A perfect positive correlation is of value +1. A good example of perfect positive correlation of +1 is the case where you use X grams of flour to make Y grams of Cake. As X increases Y increases proportionally and the correlation is equal to +1.

If the straight line goes down from left to right with **higher **values of X corresponding to **lower **values of Y then the correlation is said to be negative. A perfect negative correlation is of value -1. A good example of perfect negative correlation of -1 is the case where you have X amount of money in the bank and Y amount of additional money needed to become a millionaire. As X increases Y decreases proportionally and the correlation is equal to -1.

If there is no relationship between the variables, then the plot does not look like a straight line, rather it looks “scattered” all over the XY plane. If there is no correlation between the variables then the correlation value is 0.

The correlation value thus ranges from -1 to +1. As the correlation number gets closer to +1 or -1 such as 0.8991 0r -0.9023 then the relationship is said to be stronger. If the correlation number is closer to 0 such as -0.1023 or + 0.122 then the relationship is considered to be week.

Download the six Sigma Scatter Plot Spreadsheet Template in Excel (xlsx) format

Learn all the Six Sigma Concepts explained here plus many more in just 4 weeks. Buy our Six Sigma Handbook for only 19.95$ and learn Six Sigma in just 4 weeks. This handbook comes with 4 weekly modules. Eeach module has around 250 powerpoint slides containing six sigma concepts, examples and quizzes.