AP Statistics Unit 1

individuals

objects that are described by a set of data; may be people, animals, or things

variable

any characteristic of an individual; can take different values for different individuals

categorical variable

places an individual into one of several groups or categories

quantitative variable

takes numerical values for which arithmetic operations such as adding and average make sense

distribution

tells us what values the variable takes and frequency

1st S in SOCS

spread: give the lowest and highest value in the dataset

O in SOCS

outliers: are there any values that stand out as unusual?

C in SOCS

center: approximate average value of the data (only an estimation)

2nd S in SOCS

shape: does the graph show symmetry or skewness?

symmetric; mean = median

skewed left; mean < median

skewed right; mean > median

time plot

plots each observation against the time it was measured (time is always on the x-axis)

five number summary

minimum - q1 - m - q3 - maximum

quartiles (Q1 and Q3)

Q1: middle number of the values that are less than the median

Q3: middle number of the values that are greater than the median

IQR

interquartile range; the distance between the first and third quartiles

Outliers

the 1.5 x IQR: outlier if value is more than 1.5 x IQR below the first quartile or above the third quartile

boxplot

graph of the 5 number summary

standard deviation

S or Sx: average of the squares of the deviations of the observations from their mean

z-score

numerical measurement that describes a value’s relationship to the mean of a group of values and is measured in terms of standard deviations from the mean

percentile ranking

what percentage is less than or equal to a given value in a distribution; useful for relative position

ogive

graphical representation of the cumulative relative frequency distribution for quantitative variables

density curve

area below the curve should be 100% or 1; on or above the horizontal axis