Statistical Graphs + One and Two Variable Statisitcs

Relative Frequency Formula

frequency / number of outcomes

How to do combined mean questions

1) Turn the original mean into a total

total sum = original mean x no. of values

2) Add or remove the unknown

if a no is added → new total = total sum + x

if a number is removed → new total = total sum - x

3) new mean = new total / new no of values

4) find the unknown!

Linear correlation relationship

non-linear correlation relationship

which strength?

strong

which strength?

moderate

which strength?

weak

pos or negative?

postitive

Number data

data which can be written as numbers

Discrete numerical data

takes exact number values, and results from counting

Continuous numerical values

within a continuous range, and usually results from measuring (eg. time, height)

What is this?

Bar chart

What is this?

Pictogram

What is this?

Pie Chart

how to find a sector of a pie chart?

sector angle = value/total x 360

what is this

multiple bar chart

what is this

composite bar chart

population

is a collection of individuals or objects about which we want to draw conclusions

cenus

process of collecting data from the whole population

sample

a group of individuals from the population

survery

process of collecting data from a sample

quantitative varible

data is given in number form, is often called a numerical variable, info collected is called numerical data

quantitative can be

discrete or continous

discrete quantitative variable

takes exact number values, usually a result of counting

continuous quantitative variable

any numerical value with a certain range, usally a result of measuring

How to construct a stem plot

firstly unordered stem plot and then CAREFULLY order the stem plot

what is this? distribution

symmetrical

what is this? distribution

positivity skewed

what is this? distribution

negatively skewed

group discrete data

we group the data into class intervals

continuous data

organised using class intervals, commonly use a frequency histogram (no gaps)

modal class

the class of values that appears most often, on a freq histogram the modal class has the highest bar

mode

most frequently occurring value in the data set

mean

mean = sum of all data values / the no. of data values

median

middle value of an ordered-data set (n+1)/2

range =

maximum - minimum

quartiles + interquartile range

the median divides the ordered data set into two halves and these halves are divided in half again by the quartiles

interquartile range

the range of the middle half of the data

interquartile = upper quartile - lower quartile = Q3 - Q1

estimating the center of data in class intervals

find the midpoint

cumlative frequency

gives a running total of the scores up to a particular value, total frequency up to that value, nth percentile is the score value n% if the data lies at or below

comparing distributions of equal size

percentile = (cumulative frequency / number of data) x 100%

line of best fit by eye

1) find the mean of x and y

2) plot the mean point on the diagram

3) draw a line through the mean, have as many points below and above it

extrapolation + interpolation

interpolation - between the poles, it is reasonable to interpolate between the poles

extrapolation, outside the poles to estimate a point, is unreliable to extrapolate outside them

linear regression, line of best fit on calculator

lists & spreadsheet: enter x values into a + name it and put the y values into b and name the list

add calculator

6 stats

1 stat calcs

3 linear regression (mx+b)