### 13 April (Stem-and-Leaf Task): Which part of the Singapore Island has the best air quality?

Singapore is a garden city with trees planted all over the island to create a green belt that 'regulates' the quality of air in the Singapore island in a 'natural' manner. However, there would be a few days in a year where the quality of the air is affected by the forest fires in the nearby countries:

Reported in the ChannelNewsAsia.com website:
http://www.channelnewsasia.com/stories/singaporelocalnews/view/1087523/1/.html

http://www.channelnewsasia.com/stories/singaporelocalnews/view/1088509/1/.html

PSI stands for 'Pollutant Standards Index'. It is an index developed by the United States Environmental Protection Agency (USEPA) to provide accurate, timely and easily understandable information about daily levels of air pollution.

Every year, the quality of air in Singapore in months like October is badly affected by forest fires, when compared to other months (when we heard little about such instances taking place in the nearby region).

An estate agent claims that no matter how "polluted" the air is, "Air quality in the eastern part of Singapore is always better than that in the western part of the island." Therefore the price of housing properties at East Coast area is higher than those in Boon Lay.

On the other hand, residents who lived in Singapore over the past 5 years claim that the air quality has worsened over the years, especially in the month of October.

We are going to analyse the data available at the Singapore National Environment Agency (NEA) to help us find out whether the claims are justifiable.

Groups 1A & 1B:
Focus on the first claim "Air quality in the eastern part of Singapore is always better than that in the western part of the island."
• You are going to make comparison between 2 sets of data: PSI values for October 2010 and March 2011.
• October 2010 data: Compare the PSI values in the east and PSI values in the west
• Illustrate the data using a stem-and-leaf diagram
• Identify the mode and median PSI value in each area
• Compute the mean PSI value in each area
• Compare the data between the eastern and the western parts of the island. What can you conclude about the quality of air between the 2 areas in the month of October?
• March 2011 data: Compare the PSI values in the east and PSI values in the west
• Illustrate the data using a stem-and-leaf diagram
• Identify the mode and median PSI value in each area
• Compute the mean PSI value in each area
• Compare the data between the eastern and the western parts of the island. What can you conclude about the quality of air between the 2 areas in the month of October?
Groups 2A & 2B:
Focus on the second claim "Air quality has worsened over the years, especially in the month of October"
• You are going to make comparison between 2 sets of data: PSI values for 2005 and 2010.
• October 2005 & 2010 data: Compare the overall PSI values for both years
• Illustrate the data using a stem-and-leaf diagram
• Identify the mode and median PSI value for each year
• Compute the mean PSI value for each year
• Compare the data between 2 years. What can you conclude about the quality of air between the 2 years in the month of October?
• March 2005 & 2010 data: Compare the overall PSI values for both years
• Illustrate the data using a stem-and-leaf diagram
• Identify the mode and median PSI value for each year
• Compute the mean PSI value for each year
• Compare the data between 2 years. What can you conclude about the quality of air between the 2 years in the month of March?
Instructions to complete the work
• Each group is divided into 2 sub-groups, with 2-3 members handling each part.
• You will draw up the Stem-and-Leaf diagram on the A3 paper provided [5 min]
• Pen down the mean, median and mode below each set of data for the ease of comparison [5 min]
• Compare the data to come up with a conclusion about the quality of air. Pen down your conclusion on the paper [5 min]
• Compare the data and averages between the 2 sheets of data [5 min]
• What can you conclude and say about the 'claim'? Does your data show that the claim is justifiable?
• One spokesperson to be appointed to share the findings [5 min]

• The leader will post photos of the A3 sheets, together with the group's conclusion in the Maths blog
• Post title: (Group Name) Air Quality in the East is better than the West?
• In the post:
• Include names of the members