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Revision of skills

Mean The mean of a set of data is the most widely used average. To find the mean you add up all the values and then divide by the total number of values. Mean = sum of values number of values Calculate the mean the mean number of days it rained:

Median The median of a set of data is the middle value when all the values have been put in numerical order. Find the Median for the following 2 sets of data: 9, 15, 14, 7, 6, 13, 8 10, 8, 6, 7, 4, 12, 10,19

Mode The mode is the value which appears most often in a set of data. Find the mode values for the following sets of data: 65%, 89%, 57%, 55%, 56%, 65%, 71%, 73% 55%, 71%, 82%, 55%, 64%, 71%, 59%

In the assessment you may be asked why you selected a certain average to use. Advantage Disadvantage Most appropriate data Mean All the data is used Very large or very small numbers can distort the result Measuring temperatures, heartbeats per minute, goods produced and student’s test grades. Median Very large or very small numbers don’t affect it Doesn’t use all the data Typical salaries or house prices as it isn’t affected by extreme values. Mode Is not affected by extreme values and is the only average used to describe non-numerical data Doesn’t use all the data. There can be more than 1 mode or no mode When you need to know popular sizes or colours for buying stock.

Range The range gives a measure of how spread out the values are in a set of data. The range is the difference between the highest and lowest values. In a golf competition 8 players scored the following: 71, 73, 63, 83, 75, 85, 65, 69. Find the range of scores

Representing Data in a Bar Chart Every bar chart needs: An title that shows clearly what data the chart is representing. Labels on both the axes. An appropriate scale that shows in a clear and graphic way the data. Typical scales go up in numbers such as 1, 2, 5, 10, 20, 50, 100…

Pie Charts Pie charts are typically used to represent data that shows a share of something, such as the market share for a product or the types of weather for a year. A pie chart shows how something is divided into parts. When drawing a pie chart by hand you need to represent each part as a proportion of a circle. To do this you must divide 360 ° by the total frequency because there are 360 ° in a circle.

Scatter diagrams Scatter diagrams are used to represent two sets of data. By examining the graph, you can then decide if there is any connection between the two sets of data. You plot the data by marking where the points meet up from the x and y axis. When a scatter graph shows correlation between the two sets of data, what is called a ‘line of best fit’ can be drawn to highlight the trend of data.

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Individual study/ assessment prep