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MAL-001 – BAR GRAPHS. AND PIE CHARTS. Representing and interpreting data. MAL-001 STATISTICS. 2 Pie charts. 1 Bar charts. Bar Charts and Pie Charts. Bar Chart :
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MAL-001 – BAR GRAPHS AND PIE CHARTS
Representing and interpreting data MAL-001 STATISTICS 2 Pie charts 1 Bar charts
Bar Charts and Pie Charts Bar Chart : A graphical representation of a categorical data set in which a rectangle or bar is drawn over each category or class. The length of height of each bar represents the frequency or percentage of observations or some other measure associated with the category. The bars may be vertical or horizontal. The bars may all be the same color or they may be different colors depicting different categories. Additionally multiple variables can be graphed on the same bar chart.
Constructing Bar Charts Define the categories for the variable of interest. For each category, determine the appropriate measure or value. For a column bar chart, locate the categories on the horizontal axis. The vertical axis is set to a scale corresponding to the values in the categories. For a horizontal bar chart, place the categories on the vertical axis and set the scale of the horizontal axis in accordance with values in the categories. Then construct bars, either vertical or horizontal, for each category such that the length or height corresponds to the value for the category.
Bar charts can be used to display categorical or non-numerical data. For example, this bar graph shows how a group of children travel to school. Bar charts for categorical data
Bar charts can be used to display discrete numerical data. For example, this bar graph shows the number of CDs bought by a group of children in a given month. Bar charts for discrete data
Two or more sets of data can be shown on a bar chart. For example, this bar chart shows favourite subjects for a group of boys and girls. Bar charts for two sets of data
Give the bar chart a title. Use equal intervals on the axes. Label both the axes. Leave a gap between each bar. When drawing bar chart remember: Drawing bar charts
Bar graphTwenty four students of the class were asked the name of their favorite subject. The results are shown in the following table. Represent the given data on the bar graph
Year Number of absences 7 74 8 53 9 32 10 11 11 10 Q.1 Use the data in the frequency table to complete a bar chart showing the number of children absent from school from each year group on a particular day. Drawing bar charts
Exercises • Two hundred students of a school were asked to name their favorite color so as to decide upon what should be the color of their school building. The results are shown in the table. Represent the data on bar graph. From the bar graph answer the following questions. • Which is the most preferred color and which is the least preferred? • How many students have chosen white as their favorite color?
A test was conducted on water resistant watches made by different companies. Each of these companies claimed that their watches were water resistant . After the test the results were as shown in the graph. Write the data in tabular form. Which company has better watches?
Representing and interpreting data 2. Pie charts
Pie Chart A graph in the shape of a circle. The circle is divided into “slices” corresponding to the categories or classes to the displayed. The size of each slice is proportional to the magnitude of the displayed variable associated with each category or class. Constructing Pie Charts: Define the categories for the variable of interest. For each category, determine the appropriate measure or value. The value assigned to each category is the proportion the category is to the total for all categories. Construct the pie chart by displaying one slice for each category that is proportional in size to the proportion the category value is to the total of all categories.
A pie chart is a circle divided up into sectors which are representative of the data. Pie charts In a pie chart, each category is shown as a fraction of the circle. For example, in a survey half the people asked drove to work, a quarter walked and a quarter went by bus.
This pie chart shows the distribution of drinks sold in a cafeteria on a particular day. Pie charts Altogether 300 drinks were sold. Estimate the number of each type of drink sold. Coffee: 75 Soft drinks: 50 Tea: 175
These two pie charts compare the proportions of boys and girls in two classes. Pie charts Dawn says, “There are more girls in Mrs Payne’s class than in Mr Humphry’s class.” Is she right?
To draw a pie chart you need a compass and a protractor. The first step is to work out the angle needed to represent each category in the pie chart. Drawing pie charts This is done by working out what fraction of the total we want to represent and multiply it by 360 degrees.
For example, 30 people were asked which newspapers they read regularly. The results were : Drawing pie charts
8 7 × 360º = × 360º = 30 30 Method: Write each category as a fraction of the whole and find this fraction of 360º. Drawing pie charts 8 out of the 30 people in the survey read The Guardian so to work out the size of the sector we calculate 96º 7 out of the 30 people in the survey read the Daily Mirror so to work out the size of the sector we calculate 84º
Newspaper No of people Working Angle 6 3 7 8 6 The Guardian 8 × 360º 30 30 30 30 30 Daily Mirror 7 × 360º The Times 3 × 360º The Sun 6 × 360º Daily Express 6 × 360º Total These calculations can be written into the table. Drawing pie charts 96º 84º 36º 72º 72º 30 360º
Once the angles have been calculated you can draw the pie chart. Start by drawing a circle using a compass. Drawing pie charts The Daily Express The Guardian Draw a radius. 72º Measure an angle of 96º from the radius using a protractor and label the sector. 96º 72º 84º The Sun 36º The Daily Mirror Measure an angle of 84º from the the last line you drew and label the sector. The Times Repeat for each sector until the pie chart is complete.
Total 36 Q.1 Use the data in the frequency table to complete the pie chart showing the favourite colours of a sample of people. Drawing pie charts Favouritecolour No of people Red 10 Yellow 3 Blue 14 Green 5 Purple 4
Holiday destination No of people UK 74 Europe 53 America 32 Asia 11 Other 10 Total 180 Q.2 Use the data in the frequency table to complete the pie chart showing the holiday destinations of a sample of people. Drawing pie charts
Smokey bacon Prawn cocktail 35º 55º Salt and vinegar 135º 85º Ready salted 135 = 50º 360 Cheese and onion Q.3 The following pie chart shows the favourite crisp flavours of 72 children. How many children preferred ready salted crisps? Reading pie charts The proportion of children who preferred ready salted is: 0.375 The number of children who preferred ready salted is: 0.375 × 72 = 27