statistics gcse edexcel chapter 2 summary

statistics chapter 2 summary (grouping)

• Tally charts and frequency tables
• 1.) A tally chart or frequency table can be used to process raw data. They make it easier to spot patterns.
• Cumulative frequency tables
• 2.) The cumulative frequency of the value of a variable is the total number of observations that are less than or equal to that value.
• Grouping discrete data
• 3.) If data is widely spread it should be grouped into classes.

statistics chapter 2 summary (tables)

• Classes of varying width and open-ended classes
• 4.) When there is an uneven spread of data across the range, class intervals may vary in width.
• 5.) When the extreme values of data are not known, the first and/or last intervals may be left open.
• Two-way tables
• 6.) A two-way table displays frequencies for two categories of data.
• Other tables and databases
• 7.) A database is an organised collection of information.
• 8.) A summary table shows data that has been sorted and summarised. It is easier to interpret than the original data.

statistics chapter 2 summary (pictograms)

• 9.) A pictogram uses symbols or pictures to present a certain number of items.
• 10.) It must have a key to tell you the number of items represented by a single symbol or picture.
• 11.) When drawing a pictogram, make sure that;
• Each picture is the same size
• The picture can be divided easily to show different frequencies
• The spacing between the pictures is the same in each row
• You give a key

statistics chapter 2 summary (bar charts)

• 12.) In a bar chart, bars of equal width are drawn for each category or quantity.
• 13.) The length of a bar is equal to the frequency of the category it represents.
• 14.) The gaps between bars must be of equal width.
• Vertical line graphs
• 15.) A vertical line graph is similar to a bar chart except that the bar width is reduced to a pencil line thickness.

statistics chapter 2 summary (diagrams)

• Stem and leaf diagrams
• 16.) A stem and leaf diagram shows the data distribution in the same way as a bar chart but it retains the details of the data.
• 17.) A key shows how the stem and the leaves are combined to form a number.
• Pie charts
• 18.) A pie chart is a way of displaying data when you want to show how something is shared or divided.
• 19.) A pie chart uses area to represent frequency. The angles at the centre of a pie chart add up to 360o.
• Using bar charts to make comparisons
• 20.) Multiple bar charts have more than one bar for each class.
• 21.) Each bar in a composite bar chart shows how the total frequency for each category is made up from the separate component groups.
• 22.) The total frequencies and the frequencies of each of the component groups can be compared.

statistics chapter 2 summary (comparision)

• Using pie charts to make comparisons
• 23.) Comparative pie charts can be used to compare two sets of data.
• 24.) The area of the two circles should be in the same ratio as the two total frequencies.
• 25.) r2 = r1 √ F2
• √ F1
• Where r1 = radius of first circle
• r2 = radius of second circle
• F1 = total frequency of the first data set
• F2 = total frequency of the second data set
• 26.) To compare the total frequencies, compare the areas.
• 27.) To compare proportions, compare the individual angles.