Averages and measures of spread Flashcards

1
Q

median equation

A

(n+1) /2

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2
Q

normal distribution

A

mean and median approximately equal

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3
Q

positive skew

A

mean greater than median (peaks to the left)

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4
Q

negative skew

A

mean less than median (peaks to the right)

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5
Q

what to use for ordinal categorical or continuous variables

A

mean or median

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6
Q

what to use for categorical nominal variables

A

no sense to use median or means

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7
Q

what’s a factor

A

when there’s 2 category variables

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8
Q

how to know what analysis to use

A

if both are categorical use a contingency table
if group and continuous compare means/medians

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9
Q

percentile

A

value at or below which a specified percentage of the scores in the distribution fall
eg 60th %tile = 60% of observations lie at or below and 40% at or above

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10
Q

percentile calculation

A

value of percentile = (percentile/100) x (n+1)th

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11
Q

25th percentile

A

lower quartile

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12
Q

50th percentile

A

median

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13
Q

75th percentile

A

upper quartile

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14
Q

lowest quintile

A

lowest 20%

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15
Q

highest quintile

A

highest 20%

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16
Q

lowest decile

A

lowest 10%

17
Q

highest decile

A

highest 10%

18
Q

lowest tertile

A

bottom third

19
Q

highest tertile

20
Q

measures of spread

A

range
interquartile range
standard deviation
variance

21
Q

interquartile range

A

diff between upper and lower quartile

22
Q

variance equation

A

sd squared

23
Q

lower fence equation

A

LQ - (1.5xIQR)

24
Q

upper fence equation

A

UQ + (1.5xIQR)

25
residual
difference between a particular observation and mean
26
standard deviation in relation to residual
square root of sum of squared residuals or in statistical jargon
27
sd equation
square root of sum of (y-mean)2 / n-1