chapter 37 presentation of data 2. learning objectives read from a time-series graph read from a...
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Chapter 37Chapter 37
Presentation of Data 2Presentation of Data 2
Learning ObjectivesLearning Objectives Read from a time-series graphRead from a time-series graph Draw a time-series graphDraw a time-series graph Calculate moving averagesCalculate moving averages Draw a moving average graphDraw a moving average graph Draw a trend lineDraw a trend line Read from a trend lineRead from a trend line Read from a histogramRead from a histogram Draw a histogram Draw a histogram Draw a frequency polygonDraw a frequency polygon Recognise misleading graphsRecognise misleading graphs
Time-SeriesTime-Series
Time always goes along the bottomTime always goes along the bottom
ExampleExample
The temperature of a patient taken The temperature of a patient taken every half hour is:every half hour is:
TimeTime 09309300
10010000
10310300
11011000
11311300
12012000
Temp-Temp-eratureraturee
36.936.9 37.137.1 37.637.6 37.237.2 36.536.5 3737
Moving AveragesMoving Averages Gives an idea of Gives an idea of
the trend taking the trend taking out seasonal out seasonal variationsvariations
ExampleExample
Calculate the moving Calculate the moving averages in the averages in the following gas units following gas units used by a familyused by a family
Gas UsedGas Used
YearYear QuarterQuarter UnitsUnits19981998
19991999
20002000
11
22
33
44
11
22
33
44
11
22
33
44
345345
4949
3030
188188
277277
3737
4646
260260
319319
4545
5050
232232
Moving Average GraphMoving Average Graph
The moving average must be plotted The moving average must be plotted at the centre of the groupat the centre of the group
The trend line is a line of best fit The trend line is a line of best fit through these pointsthrough these points
Moving Averages Graph for Moving Averages Graph for Gas UnitsGas Units
181614121086420-2
400
300
200
100
0
-100
181614121086420-2
400
300
200
100
0
-100
181614121086420-2
400
300
200
100
0
-100
181614121086420-2
400
300
200
100
0
-100
Quarter
1 2 3 4 1 2 3 4 1 2 3 4
1998 1999 2000
Amount of Gas Used (Units)
Frequency DiagramsFrequency Diagrams
Bar Chart – no groups – gaps - Bar Chart – no groups – gaps - discretediscrete
Bar Chart – groups – no gaps – Bar Chart – groups – no gaps – histogram - continuoushistogram - continuous
Frequency Polygon (Diagram)– join Frequency Polygon (Diagram)– join up the mid-points of the top of the up the mid-points of the top of the barsbars
Frequency PolygonFrequency Polygon
This table shows This table shows the heights of the heights of some girlssome girls
HeightHeight FreqFreq
130130≤h<140≤h<140
140140≤h<150≤h<150
150150≤h<160≤h<160
160160≤h<170≤h<170
170170≤h<180≤h<180
33
55
1212
44
11