Scatter Diagrams Final

8/9/2019 Scatter Diagrams Final

1/17

SCATTER DIAGRAM

Presented by -:

Tejashree desai- 12

Sweta gala- 14

Mansi patel- 38Jignesh rathod- 45


2/17

What it is ?A scatter diagram is a tool for analyzing relationships

between two variables. One variable is plotted on thehorizontal axis and the other is plotted on the verticalaxis.

The pattern of their intersecting points can graphicallyshow relationship patterns.

Most often a scatter diagram is used to prove ordisprove cause-and-effect relationships. While thediagram shows relationships, it does not by itself provethat one variable causes the other.

In addition to showing possible cause and effectrelationships, a scatter diagram can show that twovariables are from a common cause that is unknown orthat one variable can be used as a surrogate for theother.


3/17

When to use it ?

Use a scatter diagram to examine theories

about cause-and-effect relationships and tosearch for root causes of an identified problem.

Use a scatter diagram to design a control

system to ensure that gains from quality

improvement efforts are maintained.


4/17

How to use it ?Collect data. Gather 50 to 100 paired samples of

data that show a possible relationship.

Draw the diagram. Draw roughly equal

horizontal and vertical axes of the diagram,

creating a square plotting area.

Label the axes in convenient multiples (1, 2, 5,

etc.) increasing on the horizontal axes from left to

right and on the vertical axis from bottom to top.

Label both axes.

Plot the paired data. Plot the data on the chart,

using concentric circles to indicate repeated data

points.


5/17


6/17

SCATTER DIAGRAM

InterpretingThem


7/17

Interpret the data : Scatter diagrams will generally show one of

six possible correlations between the variables:

StrongPositive CorrelationThe value of Y clearly increases as the

value of X increases.

StrongNegative CorrelationThe value of Y clearly decreases as

the value of X increases.

Weak Positive CorrelationThe value of Y increases slightly as the

value of X increases.

Weak Negative CorrelationThe value of Y decreases slightly as

the value of X increases.

Complex CorrelationThe value of Y seems to be related to the

value of X, but the relationship is not easily determined.

No CorrelationThere is no demonstrated connection between the

two variables.


8/17


9/17


10/17


11/17


12/17


13/17


14/17

JohnBettySarah PeterFionaCharlie Tim GerryMartineRachel

Maths score 72 65 80 36 50 21 79 64 44 55

English

score78 70 81 31 55 29 74 64 47 53

Here is a table showing the results of two examinations set to students

that I teach. I set them a maths exam and an English exam and record

the scores that they get in both:

We take a piece of graph paper and draw two axes. The horizontal axis willrepresent the score on the English exam. The vertical axis will represent the

score on the Maths exam. For each student, we then mark a small dot at the co-

ordinates representing their two scores.


15/17

The fact that the points lie close to the straight line is called a strong correlation. The

fact that this line points upwards to right - indicating that the English mark tends to

increase as the maths mark increases - is called a positive correlation.


16/17

LESSON OBJECTIVE

To be able to interpret Scatter Diagrams

To understand the terms Correlation and the

Line of Best Fit


17/17

The relationship between two variables is called aCorrelation

A line of best-fit is a line which helps us to identifythe type of correlation (positive, negative, nocorrelation) & make predictions

The line of best fit is drawn so that the points areevenly distributed on either side of the line

The closer the dots to the line, the stronger thecorrelation

Remember:

1. The line of best fit is a STRAIGHT LINE

2. It DOES NOT have to pass through the origin

3. It DOES NOT have to go through each point

Conclusion:

Scatter Diagrams Final

Documents

Transcript of Scatter Diagrams Final