Measures of central tendency and dispersion Flashcards

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1
Q

What is central tendency ?

A

Measure averages which tell us about the most typical values.

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2
Q

What are the three main types of central tendency ?

A
  • Mean
  • Median
  • Mode
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3
Q

Mean

A
  • often known as the average
  • Calculated by: adding up all the values and dividing it by the amount of scores
  • strength - most representative as it includes all the values
  • Limitation - easily distorted by extreme values
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4
Q

Media

A
  • The middle number in a data set when the socres are arranged from lowest to highest
  • stregth - extreme scores have no effect
  • strength - easily calculated
  • limitation - actual values of lower and higher figures are ignored
  • limitation - the extreme values may be important
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5
Q

Mode

A
  • The most frequently occurring value in a data set
  • There can be two-modes (bi-modal) or no modes
  • strength - easy to calculate
  • limitation - not representative
  • limitation - if bi-modal - the two modes can be very different
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6
Q

What are the measure sof dispersion ?

A

Any measure of the spread or variation in a set of scores

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7
Q

What are the two types of measures of dispersion ?

A
  • range
  • standard deviation
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8
Q

Range

A
  • A calculation of the spread of the scores
  • Taking the highest number away from the lowest +1
  • Adding 1 is a mathematical correction as raw scores are often rounded up
  • Strength - easy to calculate
  • Limitation - only looks at the two most extreme values (unrepresentative)
  • Limitation - doesn’t indicate whether numbers are closely groups or very spread out values
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9
Q

Standard deviation

A
  • ‘More sophisticated’ measure of dispersion
  • tells us how much as single value deviates from the mean
  • larger standard deviation = more dispersion, this suggests not all participants are affected by the independent variable may be a few anomalous results)
  • low standard deviation means that the participants were affected similarly
  • Strength - more precise than the range
  • Limitation - can be distorted by an extreme value
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