Lesson 21
Questions that test students on the analysis of data
Scenario: During the month of June 2013, Singapore was
affected by the Haze problem from Sumatra. The figure 1.1 below shows the
satellite image of how has the haze affected Singapore. The dots represent the
fire hotspot while the white streaks represents the smoke emitted due to the
hotspot.
Fig. 1.1
The data for the number of hotspots for each day is given in
figure 1.2 below.
|
Date
|
Number of hotspots
|
|
Date
|
Number of hotspots
|
|
31-May
|
48
|
|
15-Jun
|
101
|
|
1-Jun
|
33
|
|
16-Jun
|
138
|
|
2-Jun
|
9
|
|
17-Jun
|
113
|
|
3-Jun
|
5
|
|
18-Jun
|
187
|
|
4-Jun
|
6
|
|
19-Jun
|
173
|
|
5-Jun
|
53
|
|
20-Jun
|
85
|
|
6-Jun
|
85
|
|
21-Jun
|
21
|
|
7-Jun
|
82
|
|
22-Jun
|
118
|
|
8-Jun
|
36
|
|
23-Jun
|
227
|
|
9-Jun
|
7
|
|
24-Jun
|
437
|
|
10-Jun
|
13
|
|
25-Jun
|
174
|
|
11-Jun
|
5
|
|
26-Jun
|
59
|
|
12-Jun
|
3
|
|
27-Jun
|
42
|
|
13-Jun
|
22
|
|
28-Jun
|
15
|
|
14-Jun
|
46
|
|
29-Jun
|
7
|
Fig. 1.2
(a) Plot a graph
of number of hotspots against the day. [3]
[5 marks: 3 marks for correct
plotting of points (minus 1 mark for each mistake); 2 marks for labeling of the
x and y-axis]
(b) The daily graph that you have plotted above
may show some anomalous (irregular) trend. State the anomaly and suggest what
could have caused it. [2]
The anomaly is on the 21st
of June 2013. It shows a dip in hotspot but the hotspot numbers increases
suddenly 3 days later to 437 hotspots.
The cloud and smoke cover could
have caused a miscount on the 21 June 2013.
[2 marks – 1 mark for statement; 1 mark for explanation]
(c) Fig 1.3 below shows how the PSI value
changes with time on 20th June 2013.
Fig. 1.3
A student suggest that it is not possible for the current
PSI value at 6 pm to be 457 while the 3-hour average PSI was at 310. State and
explain whether the claim made was valid.
The claim was NOT valid.
The 3-hour average PSI was
calculated using the PSI values from the last 3 hours. Using the data from the
graph, the last 3 hours of data were:
6 pm – PSI 457
5 pm – PSI 252
4 pm – PSI 222
Taking the average, the answer is
(457+252+222)/3 = 310, which is correct.
[3 marks – 1 mark for claim, 1 mark for using the data, 1
mark for showing the calculation to arrive at the answer]
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