Interpreting Graphs and Diagrams

Interpreting Graphs and Charts

Reading Charts

Bar Charts, Pictograms & Pie charts

Pictograms

• Uses picture icons

• Shows total for each person

Understanding :

• Mike makes a pictogram for the goals scored by players on the local football team.

  
  

• Tim scored 8 goals, Dwayne scored 12 goals, Mark scored 4 goals & Jay scored 8 goals.

  
  

• How could we make the pictogram easier to draw?

  
  

Understanding:

• Find the key - you need to know what the icon means.

• Look at the icon - what does half of the icon mean

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Bar Charts

Each category has a separate bar.

The height of the bar shows the total for each.

Multiple Choice

The shop sold 10 pairs of shoes.

(Hover over the image to enlarge it)

• True

• False

The shop sold 10 pairs of shoes

This is FALSE because

the bar reaches up to 8 on the frequency scale.

Multiple Choice

The shop sold three hats.

(Hover over the image to enalrge it)

• True

• False

The shop sold three hats.

This is TRUE because

the bar for hats reaches 3 on the frequency scale.

Multiple Choice

The shop sold 6 more T-shirts than hats.

(Hover over the image to enlarge it)

• True

• False

The shop sold 6 more T-shirts than hats

This is TRUE because

the number of hats is 3 and the number of t-shirts is 9.

3 + 6 = 9

Multiple Choice

The shop sold double the amount of shorts than hats.

(Hover over the image to enlarge it)

• True

• False

The shop sold double the number of shorts to hats.

This is FALSE because

there are 3 hats and there are 7 shorts.

Double 3 is 6 not 7.

Multiple Choice

In total the shop sold 25 items.

(Hover over the image to enlarge it)

• True

• False

The shop sold a total of 25 items.

This is FALSE because

Shoes = 8, T-shirts = 9, Hats = 3 and shorts = 7.

8 + 9 + 3 + 7 = 27 , not 25

Remember this?

A) 18 people in 6 sections

3 students per section.

Blue = 3

B) 40 people in 8 sections

5 students per section

Green = 15

C) 50 people in 10 sections

5 students per section

Yellow = 40

Remember this?

If the pie chart does not have equal sections you need to use 360 degrees as equal sections.

We can now think of the coloured section as a fraction of the circle.

Multiple Choice

What fraction of the pie chart is shaded?

(hover over the image to enlarge it)

Why is the correct answer ¹³⁵/₃₆₀ ?

• The coloured shape is 135 degrees.

• There is a total of 360 degrees

Now its a fractions question:

• calculate ¹³⁵/₃₆₀ of 400 students.

• ⁴⁰⁰ / ₃₆₀ x 135 = 150

• ¹³⁵ / ₃₆₀ x 400 = 150

Try these:

• how many people are in the shaded sections for each question?

How did you do?

• A) ⁶⁰/₃₆₀ is the fraction of the pie chart.

• ⁶⁰/₃₆₀ x 120 = 20

• D) ¹⁶⁰/₃₆₀ is the fraction of the pie chart.

• ¹⁶⁰/₃₆₀ x 180 = 80

Try these

how many people are in the shaded sections for each question?

Fill in the Blanks

Answer 42

²¹⁰ / ₃₆₀ x 72

Fill in the Blanks

Answer 495

⁸¹ / ₃₆₀ x 2200

Time Series Graphs

These are line graphs that give information over time.

This graph is about the temperature during th day.

Question 1

• What is the temperature at 1am?

• 9^oC

Question 2:

• Between what times is the temperature rising?

• The temperature is rising between 04:00 and 15:00.

Question 3:

• At what times is the temperature 18^oC ?

• The temperature is 18^oC at 13:00 and 16:00 - 17:00

Question 4:

• Use the graph to estimate the temperature at 16:30.

• at 16:30 the temperature is approximately 18^oC.

The plotted points:

• The table of information is a set of co-ordinates to be plotted.

• It is clear that (50,5) is an outlier because it doesn't seem to fit the pattern of points.

• Not including the outlier this means that the correlation is positive.

Why draw a line of best fit?

• A line of best fit gives us an idea of the "general pattern" of the points.

• The line of best fit is essential for estimating missing results

• If you are not directed to draw a line of best fit - draw one anyway!

Use your line of best fit to estimate:

• Khan plans a ride for 35 minutes, how far will he expect to go?

• Find 35 minutes, read to the line and then across to distance.

• Be ready to ESTIMATE from the scale. This example is approximately 17km.

Reliable Estimates?

Lite mobile recorded the price and sales of its phones and plotted a scatter diagram.

1) How many sales of £100 phones were there?

2) How many sales of £250 phones were there?

Reliable Estimates?

1) How many sales of £100 phones were there? 410

2) How many sales of £250 phones were there? 300

Which estimate is the most reliable?

Reliable Estimates?

Estimating for £100 IS reliable because it is INTERPOLATING within the data points we know.

Estimating for £200 IS NOT reliable because it is EXTRAPOLATING outside the data points we know.

Your teacher should have set you assignments on

Pie Charts

Scatter Diagrams