Averages and measures of spread

Question 1

median equation

Answer 1

(n+1) /2

Question 2

normal distribution

Answer 2

mean and median approximately equal

Question 3

positive skew

Answer 3

mean greater than median (peaks to the left)

Question 4

negative skew

Answer 4

mean less than median (peaks to the right)

Question 5

what to use for ordinal categorical or continuous variables

Answer 5

mean or median

Question 6

what to use for categorical nominal variables

Answer 6

no sense to use median or means

Question 7

what’s a factor

Answer 7

when there’s 2 category variables

Question 8

how to know what analysis to use

Answer 8

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

Question 9

percentile

Answer 9

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

Question 10

percentile calculation

Answer 10

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

Question 11

25th percentile

Answer 11

lower quartile

Question 12

50th percentile

Answer 12

median

Question 13

75th percentile

Answer 13

upper quartile

Question 14

lowest quintile

Answer 14

lowest 20%

Question 15

highest quintile

Answer 15

highest 20%

Question 16

lowest decile

Answer 16

lowest 10%

Question 17

highest decile

Answer 17

highest 10%

Question 18

lowest tertile

Answer 18

bottom third

Question 19

highest tertile

Answer 19

top third

Question 20

measures of spread

Answer 20

range
interquartile range
standard deviation
variance

Question 21

interquartile range

Answer 21

diff between upper and lower quartile

Question 22

variance equation

Answer 22

sd squared

Question 23

lower fence equation

Answer 23

LQ - (1.5xIQR)

Question 24

upper fence equation

Answer 24

UQ + (1.5xIQR)

Question 25

residual

Answer 25

difference between a particular observation and mean

Question 26

standard deviation in relation to residual

Answer 26

square root of sum of squared residuals or in statistical jargon

Question 27

sd equation

Answer 27

square root of
sum of (y-mean)2
/
n-1