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Normal distribution curve
• Calculate Range
• Calculate the cell interval
• Calculate the cell boundaries and cell midpoint
• Post the cell frequency of cells boundary
• Calculate Variance
• Calculate Standard deviation
• Calculate Mean
• Calculate Median
• Calculate Mode
Steps …
R = XH - XL
• Calculate Range
R = Range
XH = highest number
XL= Lowest number
• Calculate the cell interval
H= no. of cells
I = cell interval
H = R/ I
Cell midpoint = ( upper boundary + lower boundary ) / 2
• Calculate the cell boundaries and cell midpoint
• Post the cell frequency of cells boundary
• Calculate Standard deviation
The standard deviation measures:
the spread of the data about the mean value.
It is useful in comparing sets of data which may have the same mean
but a different range.
The formula is easy: it is the square root of the Variance.
σ = √ σ2
σ2 = ( X- X )2 / n
• Calculate Variance
is defined as:
The average of the squared differences from the Mean.
it is the sum divided by the count.
X = ∑ Xi / n
• Calculate Mean
= average
Median. The median is the middle number in the data set.
For example, in the data set {1, 3, 3, 6, 7, 8, 9},
the median is 6,
What is the use of median?
However, when the sample size is large and does not include outliers,
the mean score usually provides a better measure of central
tendency.
“(Then goes on to give an example of when the median is better.)
“Use the median to describe the middle of a set of data that does
have an outlier
•Calculate Median
The mode is the most commonly occurring number in a data set
•Calculate Mode
The mode is useful when the most common item, characteristic or value of a data set is
required.
Example: in {6, 3, 9, 6, 6, 5, 9, 3}
the Mode is 6 (it occurs most often).
What is the use of Mode ?
The normal distribution
Symmetrical Shape Frequency Histogram
showing Relationship of Mean , Median , Mode
Type of Variable Best measure of central tendency
Nominal Mode
Ordinal Median
Interval/Ratio (not skewed) Mean
Interval/Ratio (skewed) Median
Summary of when to use the mean, median and mode
In statistics, that single value is called the central tendency and mean,
median and mode are all ways to describe it. ...
Range, which is the difference between the largest and smallest value in
the data set, describes how well the central tendency represents the data
It is used to :
Determine the process capability
Compare with specifications
Suggest the shape of the population
Indicate conflict in data such as gaps
distribution curveThe normal
The normal distribution curve
Symmetrical
Uni modal
Bell-shaped

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Normal distribuation curve[1]

  • 2. • Calculate Range • Calculate the cell interval • Calculate the cell boundaries and cell midpoint • Post the cell frequency of cells boundary • Calculate Variance • Calculate Standard deviation • Calculate Mean • Calculate Median • Calculate Mode Steps …
  • 3. R = XH - XL • Calculate Range R = Range XH = highest number XL= Lowest number
  • 4. • Calculate the cell interval H= no. of cells I = cell interval H = R/ I
  • 5. Cell midpoint = ( upper boundary + lower boundary ) / 2 • Calculate the cell boundaries and cell midpoint • Post the cell frequency of cells boundary
  • 6. • Calculate Standard deviation The standard deviation measures: the spread of the data about the mean value. It is useful in comparing sets of data which may have the same mean but a different range. The formula is easy: it is the square root of the Variance. σ = √ σ2
  • 7. σ2 = ( X- X )2 / n • Calculate Variance is defined as: The average of the squared differences from the Mean.
  • 8. it is the sum divided by the count. X = ∑ Xi / n • Calculate Mean = average
  • 9. Median. The median is the middle number in the data set. For example, in the data set {1, 3, 3, 6, 7, 8, 9}, the median is 6, What is the use of median? However, when the sample size is large and does not include outliers, the mean score usually provides a better measure of central tendency. “(Then goes on to give an example of when the median is better.) “Use the median to describe the middle of a set of data that does have an outlier •Calculate Median
  • 10. The mode is the most commonly occurring number in a data set •Calculate Mode The mode is useful when the most common item, characteristic or value of a data set is required. Example: in {6, 3, 9, 6, 6, 5, 9, 3} the Mode is 6 (it occurs most often). What is the use of Mode ?
  • 11. The normal distribution Symmetrical Shape Frequency Histogram showing Relationship of Mean , Median , Mode
  • 12. Type of Variable Best measure of central tendency Nominal Mode Ordinal Median Interval/Ratio (not skewed) Mean Interval/Ratio (skewed) Median Summary of when to use the mean, median and mode In statistics, that single value is called the central tendency and mean, median and mode are all ways to describe it. ... Range, which is the difference between the largest and smallest value in the data set, describes how well the central tendency represents the data
  • 13. It is used to : Determine the process capability Compare with specifications Suggest the shape of the population Indicate conflict in data such as gaps distribution curveThe normal
  • 14. The normal distribution curve Symmetrical Uni modal Bell-shaped