How to Read Graphs Charts and Tables

v Interpreting graphs and charts

v.one Difficulties in estimation

Graphs and charts are frequently used to illustrate information that is discussed in class materials or a newspaper article, so it is important to exist able to interpret them correctly. Often, the authors of an article volition attempt to emphasise the point they are trying to make by presenting the facts and figures in such a way as to confirm their argument. This is a usually used journalistic approach, which means that it is essential to examine graphs and charts used to back up arguments very carefully.

In this section we are going to await at the aspects of a graph or a nautical chart that demand to be considered in order to interpret the information correctly. We are not going to consider in item how to draw graphs or create charts, as this is not something that most people observe that they need to do.

The examples that follow have all been taken from journals and newspapers, but we have non included the manufactures from which they are taken from. Our main purpose is to explore some of the difficulties that people face in interpreting information presented in charts and graphs.

Activity fifteen

This set of line graphs appeared in an article about the transformation of the workforce over the past 2 decades. Expect at the graphs and try to respond the questions.

Source: The Guardian 4 January 1999

1. What exercise you remember 4.1m means?

2. What practise yous think 55+ means?

3. What impression do you become about the workforce anile 55+ and the manufacturing workforce?

4. Draw what appears to take happened to the female workforce in comparing to the workforce aged 55+.

5. What can you say almost the time scales of these graphs?

Discussion

1. 'm' is an abbreviation for million, so 4.1m is 4.ane million or iv 100 000 people.

2. 55+ is a short paw way of indicating all those older than 55.

3. If you lot compare the height and lesser graphs, your offset impression is likely to exist that the workforce anile 55+ has declined by much the aforementioned amount as the manufacturing workforce. However, the workforce aged 55+ has declined past 1.3m (4.1m − two.8m), which every bit a pct is a subtract of × 100, approximately 32 per cent. The manufacturing workforce has declined by three.3m and this is a per centum subtract of × 100, approximately 45 per cent. This ways that the manufacturing workforce has actually declined more significantly than the workforce aged 55+ in the last 20 years or so.

4. The impression given past the graph of the female workforce is that the number of women in piece of work has risen steadily over the last xx years, in direct dissimilarity to the workforce aged 55+. The actual increase in the female person workforce is 2.9m. As a percentage, this is × 100 which is approximately 31 per cent. Here our initial impression is the correct one.

5. The outset two graphs give figures from 1971 and the third ane starts in 1976. All three graphs have the same altitude between each year given on the graph. However, this distance should exist less when in that location is a gap of five years than when there is a gap of x years.

   The horizontal scales are not the aforementioned for each graph. It is possible that the 1976 in the third graph is a misprint but even if it is not, the horizontal scales are still misleading. Each of the graphs has the years 1981, 1991 and 1996 evenly spaced along the horizontal centrality but the intervals are not the same. 1996 should exist closer to 1991 and this would mean that each of the graphs would flatten off less.

Every graph should take a vertical and a horizontal calibration. The primary purpose of each calibration is to let the states to read the values from the graph at any point that we desire. None of these graphs take a vertical calibration, instead figures are given at intervals corresponding to the vertical calibration. If you look carefully at these figures you will see that each graph has a different vertical calibration. The peak graph goes from iv.1m to ii.8m, a divergence of one.3m, the centre graph goes from ix.4m to 12.3m, a difference of 2.9m and the bottom graph goes from seven.3m to four.0m, a divergence of 3.3m. The meridian of each of the graphs is roughly the aforementioned but every bit we can at present see, the scale is different in each example. This gives a misleading impression of the numbers involved and means that but the general tendency of each graph tin be compared. For a fairer comparing the vertical scale should be the aforementioned for all three graphs.

Activity 16

This line graph appeared in an article well-nigh the number of non-Uk registered nurses with the NHS (National Health Service). Subsequently you have looked at the graph, try to answer the questions below.

Source: The Guardian 9 Jan 1999

1. What impression exercise you remember the writer is trying to give?

2. In that location appears to be a crossover point, when did it have place?

3. How many UK nurses were registered with the NHS at this time?

4. How many EU/not-Eu nurses were registered with the NHS at this fourth dimension?

5. Describe what the bodily situation every bit regards UK and European union/not-Eu nurses was at this time.

Discussion

1. The author would like usa to believe that the number of EU/non-European union nurses registered with the NHS is now greater than the number of UK nurses registered with the NHS.

2. The crossover signal appears to have occurred some time between 1996 and 1997. However, the horizontal calibration is very difficult to read and it isn't articulate where each yr starts and finishes.

3. At the signal where the lines cross, there were approximately 25 000 UK nurses registered with the NHS.

4. At the aforementioned time, at that place were approximately 2500 EU/not EU nurses registered with the NHS.

5. Opposite to the impression given past the graphs, the number of UK nurses registered with the NHS far exceeded the number of EU/non-EU nurses also registered with the NHS. The total number of nurses registered at that time was 27 500. If we calculate the number of Eu/non-EU nurses as a per centum of the total number of nurses ( × 100) we find that they accounted for 9 per cent of the total. It is fair to say that the number of UK nurses registered is failing but the number of EU/non-Eu nurses registered has a long style to go before it over takes the United kingdom of great britain and northern ireland number.

First impressions can be very misleading. 'Nursing numbers' shows two graphs with 2 different vertical scales superimposed on 1 another. As the scales are unlike, it is incorrect to depict any conclusions from the visual impression of how the ii graphs compare to each other. A fairer picture would have been given if the same calibration had been used for both. Yet, given that the number of EU/non-Eu nurses registered with the NHS has never exceeded 5000, the resulting graph would not be very meaningful. You might like to have a go at sketching it.

Activity 17

This horizontal bar chart appeared in an article about the pros and cons of modernistic life for children. After studying it, endeavor to answer the questions that follow.

Source: The Guardian xiv Jan 1999

1. What impression do y'all get almost the number of deaths in 1948 compared with the number of children aged 17 years and under plant guilty of whatsoever criminal offence at present?

2. Practise we take any idea of the number of children living in poverty in 1948?

3. Can nosotros tell from the bar chart if the number of children living in poverty has increased or decreased since 1948?

Word

1. The bar representing the number of deaths in 1948 appears to be exactly the same in length as the bar representing the number of children found guilty of whatever offense now. If you looked at this chart speedily, you lot could easily come away with the impression that the numbers were the same in both cases. Even so, the numbers given tell a completely unlike story: the number of deaths in 1948 was 34 933, and the number of children institute guilty of any law-breaking now is 179 300.

2. The chart gives the number of children living in poverty in 1948 as ane in 4, but the number of children living in United kingdom of great britain and northern ireland in 1948 is not given on the chart. The ratio one in 4 tells us that (which is the same every bit 0.25 or 25 per cent) of the number of children living in Britain in 1948 were living in poverty.

3. No, considering we don't know the number of children. The chart gives the impression that the number has reduced equally the ratio today is ane in 5, which tells us that (which is the same every bit 0.2 or 20 per cent) of children are living below the poverty line. Since the chart does not give the number of children living in the U.k. in 1948 or now, we can't exist sure whether or non there has been a drop in the actual number of children living below the poverty line.

In order to go a feel for the bodily number of children living below the poverty line, you lot need the figures given in the article, namely that in that location were 14.five million children living in the U.k. in 1948 and there are 14.viii meg now. This makes the number of children living below the poverty line in 1948, 3.625 million ( × 14 500 000) and now there 2.96 meg ( × 14 800 000). These values are very much larger that those relating to crime and death but this is not evident when y'all kickoff look at the charts.

The three charts do not have a common scale and therefore should not be compared direct. Hither it is very important to consider each nautical chart separately, particularly every bit the information in the kickoff 1 is given as a ratio and the other two quote actual numbers. The bar for 65 000 is less than half the length of the bar for 34 933 so unless you wait at the figures advisedly, your brain can be deceived.

Action 18

This bar chart shows the number of mentions that each historic period group got in chore advertisements appearing in the Lord's day Times, The Guardian and The Telegraph during November 1995.

Source: People Management 11 January 1996

1. Which historic period grouping got the largest number of mentions?

2. Which age grouping got the fewest mentions?

3. What does this chart tell us?

4. Wait at the horizontal scale and comment on information technology.

Word

1. The age group which got the largest number of mentions is 30s.

2. The age group which got the to the lowest degree number of mentions is 28–forty.

3. The answers to the get-go 2 questions are somewhat contradictory since the age group 28–40 covers the 30s. The introduction to this example says that this chart gives the number of mentions of different age groups in job advertisements in Nov 1995. It appears that the age group given in each of the advertisements was recorded with the number of each existence recorded past this chart. In other words, the chart is simply recording how frequently each age grouping description was used.

4. The horizontal scale is simply beingness used to record the different age groups. Commonly you would await the values to increment from left to right but in this case it is hard to guild the different historic period groups. The author has called to given the age groups in descending club of the number of mentions, which gives the visual impression that the younger age groups got more mentions.

This chart actually tells us very niggling. The overall impression is that 20s, 20–30 and 30s get mentioned most and no mention is made of forty+ historic period groups orthose nether xx. Given the confused nature of the horizontal calibration, it is pointless to look for whatsoever meaningful trend in the graph. All the same, it is interesting to note that this graph appeared in an article claiming that age discrimination still exists.

Action 19

This bar chart gives the percentage of women giving birth by caesarean section since 1970. Take a look at the chart, bearing in listen the points that take been made so far.

Source: Radio Times 23–29 Jan 1999

The author of the article in which this bar chart appeared makes the following last comment in the accompanying text:

I specialist I spoke to reckons that the charge per unit could rise to over 50% within the next 20 years. A quick look at the graph suggests he could be right.

What do you think about this statement?

Discussion

You might agree, as the numbers are increasing and the projection has been drawn on the chart. Only if you look more closely at the figures given, y'all will probably feel that the projection is somewhat exaggerated. You might feel that we should be able to make a stab at what the effigy will be and this is exactly what we will now do.

In order to decide if the statement is correct we must commencement look at the horizontal scale. The interval between 1970 and 1985 is fifteen years, there are 7 years betwixt 1985 and 1992, and v years betwixt 1992 and 1997. However, there is not a regular interval between each of the years given on the chart which means that information technology is not possible to extrapolate the diagram to predict the value in 2010. The easiest way to decide what the figure might be, is to redraw the chart as a line graph with an evenly spaced scale on the horizontal axis. When we do then, we get this line graph.

Source: Radio Times 23–29 January 1999

Past extending the line drawn through the information values we were given, we tin can at present see that the possible value in 2010 might be 22%. When we consider the 20-year interval that the writer refers to, in 2019 the value merely increases to about 28%. This is somewhat less than the 50% suggested by the commodity.

The article discusses whether or non women should be immune to have a caesarean section on demand and cites evidence to show that more and more women are opting for this. Even if we allow forthe fact that the number of caesarean sections is growing more speedily now than in the 1970s or 1980s, it is non obvious from the figures that the charge per unit could rise to over 50 per cent inside the next xx years.

Activity xx

This line graph gives the age distribution of the working population in Bully Britain (GB). Later on you lot have considered it, attempt to answer the questions alongside.

Source: People Management 11 January 1996

1. What tendency do you think that this graph is trying convey?

2. Practise yous observe it like shooting fish in a barrel to interpret this graph?

Give-and-take

1. Yous may well feel that there is no obvious trend. Withal, you might have said that the graph shows that the number of people aged 44+ is going to increment. You may also have said that the other two historic period groups will see a slight drop in numbers.

2. The graph is non very easy to read. It is not immediately clear whether i is looking at the space between the lines or the three lines themselves. If nosotros consider the spaces, in 2006 the working population is predicted to be made up of almost five million people anile 16–24, about three.5 million people aged 25–44, and about 5.v million people anile 44+. This suggests that the full working population will be 14 million. However, if we consider the lines, in 2006 the working population is predicted to exist made up of about 5 million people anile 16–24, about 14 million people aged 25–44 and 10.five one thousand thousand people aged 44+. This suggests that the working population will exist 29.v million. This figure is more conceivable since the bodily working population is currently about 27.5 million.

This is an instance of how an writer can try to emphasise the point they want to make past the style that they draw the graph. Nosotros need to take slap-up care when we look at a graph or nautical chart in instance we are misled by it. The original graph also used colour to emphasise the spaces: the 16–24 space was bluish; the 44+ space bright yellow; and the 25–44 space, orangish. It would make more sense for the graph to accept the 44+ band on superlative, merely the writer has chosen to sandwich it in the center. The accompanying commodity was most age discrimination and it maybe that the author felt that by structuring the graph in this way, it highlighted the situation for the over 44s.

chowdhuryextrave1970.blogspot.com

Source: https://www.open.edu/openlearn/science-maths-technology/mathematics-statistics/working-charts-graphs-and-tables/content-section-5.1

Share this post