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Presented by -:Tejashree desai- 12
Sweta gala- 14
Mansi patel- 38Jignesh rathod- 45
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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 cangraphically show
relationship patterns.
Most often a scatter diagram is used to prove ordisprove
cause-and-effect relationships. While thediagram shows
relationships, it does not by itselfprove that 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.
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When to use it ?U
se a scatter diagram to examine theoriesabout cause-and-effect
relationships and tosearch for root causes of an
identifiedproblem.
Use a scatter diagram to design a controlsystem to ensure that
gains from qualityimprovement efforts are maintained.
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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.
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Scatter Diagrams
A Scatter Diagram is a graph of unconnected points
When drawing graphs, we must remember to do thefollowing
things:
1. Always give the graph a title
2. Always label both axis, including correct units
3. Choose a sensible scale4. Plot your points carefully (x
first, y second)
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Interpreting Them
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Interpret the data : Scatter diagrams will generallyshow one of
six possible correlations between the
variables: Strong Positive Correlation The value of Y
clearly
increases as the value of X increases.
Strong Negative Correlation The value of Y clearlydecreases as
the value of X increases.
Weak Positive Correlation The value of Y increasesslightly as
the value of X increases.
Weak Negative Correlation The value of Y decreasesslightly as
the value of X increases.
Complex Correlation The value of Y seems to berelated to the
value of X, but the relationship is noteasily determined.
No Correlation There is no demonstrated connection
between the two variables.
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John
Betty
Sarah
Peter
Fiona
Charlie
TimGerry
Martine
Rachel
Mathsscore 72 65 80 36 50 21 79 64 44 55
Englishscore
78 70 81 31 55 29 74 64 47 53
Here is a table showing the results of two examinations set
tostudents that I teach. I set them a maths exam and an English
examand 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 dotat the co-ordinates representing their two scores.
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The fact that the points lie close to the straight line is
called a strongcorrelation. The fact that this line points upwards
to right - indicating that theEnglish mark tends to increase as the
maths mark increases - is called a positive
correlation.
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A scatter diagram is a tool for analyzingrelationships between
two variables.
Most often a scatter diagram is used to prove ordisprove
cause-and-effect relationships.
Scatter diagram cannot determine the cause of such
arelationship, it can show whether or not such a
relationshipexists, and if so, just how strong it is.
The analysis produced by the scatter diagram is calledregression
analysis.
It is also used to search for root cause of an
indentifiedproblem.
Conclusion:
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Thank you
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Presented by -:Tejashree desai- 12
Sweta gala- 14
Mansi patel- 38Jignesh rathod- 45
