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John Dunn
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Lecture

# Oct 3 - central tendency.doc

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University of Alberta

Physical Education and Sport

PEDS109

John Dunn

Fall

Description

Oct 3 – Central Tendency
Computations
Proportions, percentages
Graphical representations of data
No questions on measures of central tendency
• Mean is linked to standard deviation and variability
• Mew will be the symbol used to represent population mean instead of x bar
• X bar will be used for sample mean
• Mean is the sum of x divided by n (number of scores)
• Scores of 0 arent ignored
• Deviation score – the magnitude of the difference between a raw score and
the mean
• The sum of deviation scores will all add up to 0 – some will be negative, some
will be positive
• If we change one score, the mean must change
• Adding a score that is the value of the mean, wont change the balance of the
mean
• Mean is based on every score in the data set
• The group with the largest sample size will have the largest influence on the
mean
• Linear transformation – if the class average was 57% and the prof added 8%
to every score so that the class average went up to 65%.
• If we divided all scores by 10, the mean would be divided by 10
• The value for mean and median doesn’t necessarily have to exist in your data
set • Wwill be given a data set, given a scenario and will be asked which method of
central tendency should be used – next midterm will have this
• Any computation you do for the median will be N/2!
• The median is the middle score in an ordered distribution

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