AP stats unit 1

Pie Chart

show distribution as a part of 100 used for one variable

bar graph

a graph that uses vertical or horizontal bars to show comparisons among two or more items used

segmented graph

shows percent and must add to 100 used for two variables

percent

relative frequency

count

frequency

where does the vertical axis always start

zero

mosaic graph

segmented bar graph where width of bar is proportional to group size

Histogram

a diagram consisting of rectangles whose area is proportional to the frequency of a variable and whose width is equal to the class interval.

Unimodal

having one mode; this is a useful term for describing the shape of a histogram when it's generally mound-shaped

Bimodal

two peaks

outliers

extreme values that don't appear to belong with the rest of the data

right skew

-mean > median

symetrical

looking the same on both sides mean=median

left skewed

mean > median

spread

how spread out the data range is

stem and leaf plot

A method of graphing a collection of numbers by placing the "stem" digits (or initial digits) in one column and the "leaf" digits (or remaining digits) out to the right.

dot plot

a graphical device that summarizes data by the number of dots above each data value on the horizontal axis

mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores

median

the middle score in a distribution; half the scores are above it and half are below it

Interquartile Range (IQR)

A measure of variability, defined to be the difference between the third and first quartiles.

range

the difference between the highest and lowest scores in a distribution

Standard Deviation (SD)

A measure of variability that indicates the average difference between the scores and their mean.

Variance

standard deviation squared

mean and SD

greatly affected by outliers and are non-resistant

if the graph has outliers or is skewed

use the median and IQR

if the graph is symetric

use the mean and the standard deviation

Quartile

A division of the total into four intervals, each one representing one-fourth of the total.

Q1

the median of the lower half of the data middle number of lower half median is not used

1.5 IQR rule for outliers

call an observation an outlier if it falls more than 1.5 * IQR above the third quartile or below the first quartile

IQR is

the middle 50% of the box

left skew box plot

right skew in box plot

symmetric box plot

percentile

A point on a ranking scale of 0 to 100. The 50th percentile is the midpoint; half the people in the population being studied rank higher and half rank lower.

z-score

a measure of how many standard deviations you are away from the norm (average or mean)

context

z standard deviations above/below the mean

all standard deviations have

a mean of 0

and SD of 1

multiply or divide the data

center and variability are also multiplied

shape stays constant

add or subtract the data

shape and variability stay the same

center shifts up or down

normal curve (normal distribution)

a symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68 percent fall within one standard deviation of it) and fewer and fewer near the extremes.

68-95-99.7 rule

in a normal model, about 68% of values fall within 1 standard deviation of the mean, about 95% fall within 2 standard deviations of the mean, and about 99.7% fall within 3 standard deviations of the mean

Ideal Mean

in the middle

Table A

Where you find the proportion in the body of

discrete variable

A finite integer that is countable like Number of heads in 10 coin flips, number of students in a class, number of stars in a galaxy

continuous variable

an infinite non-countable number like sound, height, weight, time