M - Statistics & Mechanics 1 - 2) Measures of location and spread Flashcards

1
Q

Formula for mean

A

x̄ = Σx/n

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2
Q

Method to find the lower and upper quartiles of discrete data

A
  1. Divide total frequency by 4 (and times by 3 for UQ)
  2. If it’s a whole number, the LQ or UQ is halfway between this data point and the one above
  3. If it’s not a whole number, round up and pick this data point
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3
Q

Formula for variance

A

σ² = Σx²/n - (Σx/n)²

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4
Q

Formula for standard deviation

A

σ = √[Σx²/n - (Σx/n)²]

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5
Q

Effect on x̄ and σ when the coding is y = x + a and y = ax

A

y = x + a:

  • Effect on x̄ → increase by a
  • Effect on σ → no change

y = ax:

  • Effect on x̄ → a times bigger
  • Effect on σ → a times bigger
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