Processing And Representing Data Flashcards
What is a database
A collection of information
What is a two way table
A table that shows information in two categories
E.g favourite drinks for boys and girls (not just people in general)
What is bivariate data
Data with two variables
What are pictograms
Tables that use images or symbols to represent a set number of items for each picture
What should you do when drawing a pictogram
Each picture needs to be the same size
Pictures can be easily divided to show different frequencies
Spacing between pictures is the same in each row
Write a key
How do you structure bar charts
Height / length of the bar shows the frequency
Bars are equal width with equal spaces between them
What is a vertical line chart
A graph that uses vertical lines instead of bars
What do you need to do when drawing multiple bar charts.
E.g a dual bar chart
A key for what each bar represents
Ensure all bars are the same length
The different bars are all in the same group and touching
What is a composite bar chart
A bar chart showing the total frequency of one category made from specific groups
The total frequency and frequencies in each group CAN be compared
What is a stem and leaf diagram
A diagram which splits numerical data into its stem and leaves
The numbers are written in numerical order
A key shows how to combine the stem and leaves to read the number
E.g 4|3 is 43
What is one benefit of a stem and leaf diagram
You can use it to show the shape of the data distribution
But
You can still see the original values
What is back to back stem and leaf diagram
Used to compare data
The stem is in the middle and two different data sets are on either side
When do you use a pie chart / what is a pie chart
Used to represent frequency
It is a way of displaying data when you want to show how something is shared / divided
The angles at the center of a pie chart add up to 360
How do you calculate the angle you need to use when drawing a pie chart
Divide 360° by the total frequency
Using this value multiply each individual frequency to find the angle
T/360 × f
What are comparative pie charts
Pie charts used to represent / compare data
The area of each pie chart is in the the same ratio as its frequencies
To compare the frequencies compare the areas
To compare proportions compare individual angles
Why are comparative pie charts used
Comparing two pie charts of the same size, but with different populations is misleading
How do you calculate the radius of your second pie chart
R is radius
F is frequency
r¹^2 : r²^2 = f¹ : f²
r²/r¹ = √f² /√f¹
r² = r¹(√f²÷√f¹)
R¹ can be any value you chose
What are population pyramids
Graphs that show the age groups in a population - usually divide by gender
How are population pyramids drawn
You have two groups (e.g male and female)
Then you have your age grouping
The center starts at 0 and increases in equal intervals going in opposite directions
Then draw out to the frequencies on each side
What is a chloropleth map
A map used to classify regions of a geographical area
Regions are shaded with an increasing depth in colour
A key shows what each colour represents
Do cholorpleth maps have to be maps
No they can be a simple diagram
What is a histogram
Similar to a bar chart but represents continuous data
Because of this there are no gaps between the lines
What is a frequency polygon
A graph that joins the top mid points of histograms
What is cumulative frequently
A running total of all the frequencies in each group
It adds up to the total frequency
What is a cumulative step polygon
A diagram using cumulative frequency plotted on upper class boundaries
It is not drawn with a smooth curve
Draw a horizontal line to the upper bound then draw a vertical line to its value
What is a cumulative frequency diagram
A diagram for grouped continuous data
The data points are drawn on the upper boundaries and a smooth curve is used to connect them
They can be used to predict values
What Is the shape of distribution
The shape formed by the bars in a histogram or by a frequency polygon
What are the 3 types of distribution
Positive skew - moat data values are on the lower end
Negative skew - most data values are on the higher end
Symmetrical - Distribution is symmetrical / it has no skew
How are histograms for unequal class widths drawn
By adjusting the height of the bars so area represents frequency
The y axis is replaced by frequency density
How do you calculate frequency densitu
Frequency / class width
Using a histogram how do you estimate the number of people above a certain value
Add all the values of (frequency density × class width)
When can you compare histograms
If they have the same class intervals and the same frequency density scales
How can graphs be made to be misleading
Scales not starting at 0
Scales that do not increase by the same value each time
Lines on a graph being drawn too thick (hard to read value)
Axes without labels
Graphs and charts without keys
Colours can be used to make some parts stand out
How can using 3D diagrams be misleading
It can make comparisons difficult
Some parts of the diagram can appear larger than others
It would be hard to see where the value should be read from
Why is separating sections of the diagram
(E.g taking out a slice of the pie chart) misleading
It makes comparisons difficult
What do bar charts and line graphs show
Trends and patterns in data - values can be read from a scale if its not too small
What do pie charts show
Proportions, but not accurate values
What do tables show
Exact values for different categories but does not show trend patterns as clearly
Why do you need to clean data
To ensure the data has no missing values
Or to ensure the data is all in the format
