Download Calculating Statistical Information

Statistics and parameters
To find out about a population we
take a sample
Statistics describe features of the sample
What
statistics do
we use?
How are they
calculated?
We use sample statistics to make
inferences about population parameters
 Proportion
 Central tendency
 Variation or spread
 Shape
 Unusual features
The Measures of Central Tendency
The Mean is easy to calculate and is also easily
understood.
BUT! It is affected by extreme values.
The Measures of Central Tendency
The Median is unaffected by extreme values,
but it is more difficult to calculate as the data
has to be ordered first.
BUT! It is UNaffected by extreme values.
The Measures of Central Tendency
The Mode is useful to manufacturers who want
to identify the most popular value.
BUT! It is not always typical of a population as a
whole.
The Measures of Central Tendency
The Mean is easy to calculate and is
understood.
BUT! It is affected by extreme values.
The Measures of Spread
The Range is the difference between the
maximum and minimum values.
The range is easy to calculate and understand.
BUT! If there are extreme values, the range
does not accurately reflect how spread out the
data values are.
The Measures of Spread
The Inter-quartile Range is the difference
between the upper quartiles and the lower
quartile and gives the range of the middle 50%
of the data.
As the extreme values are outside the middle
50% of the data, the inter-quartile range gives a
clear indication of the spread.
The Measures of Spread
The Standard deviation is a calculated measure
of spread which is shows how much variance
there is from the mean.
You can safely conclude that a set of data with
a larger standard deviation is more spread out
than a set of data with a smaller standard
deviation.