*Reference: Worksheet 4 (p2) Constructing a Stem-and-Leaf Diagram...*In the past 10 years, Singapore has experienced several "worst" haze days.

Let's complete the back-to-back stem-and-leaf diagram that shows the PSI (Pollutant Standards Index) values of the two such instances in the decade and make a comparison of these 2 haziest periods.

The PSI values of 2006 October is shown in the table below (left).

Are you able to tell the mean and mode from the stem-and-leaf diagram?

Now, visit the NEA website to find out what the PSI value of the days in June 2010.

Complete the table in the worksheet, and make a comparison between the 2 sets of data.

What are your observations?