S2A Chapter 7 More about Statistical Graphs

2009 Chung Tai Educational Press. All rights reserved. © Terminologies about Classes Lower class boundary Upper class boundary Upper and lower class limits Class width  24.5  19.5  5 Class mark 22

2009 Chung Tai Educational Press. All rights reserved. © Frequency Distribution Table Waiting Time of 100 Passengers at a Bus Stop Waiting time (min) Class boundaries (min) Class mark (min) Frequency

2009 Chung Tai Educational Press. All rights reserved. © Frequency Polygons

2009 Chung Tai Educational Press. All rights reserved. © Cumulative Frequency Table Waiting time less than (min) Cumulative frequency

2009 Chung Tai Educational Press. All rights reserved. © Cumulative Frequency Polygon

2009 Chung Tai Educational Press. All rights reserved. © Percentiles Percentile represents a given percentage of the data less than a given value.

2009 Chung Tai Educational Press. All rights reserved. © Change the cumulative frequency to percentage. For example: 74% of students got the examination scores below Percentiles 100% 90% 80% 70% 60% 50% 40% 30% 20% 10%

2009 Chung Tai Educational Press. All rights reserved. © The score of 66.4 is called the 74th percentile and is denoted by P 74. It means 74% of S2 students have scores less than If there are 200 students in total, there are 148 (74%  200) students have scores less than Percentiles

2009 Chung Tai Educational Press. All rights reserved. © Quartiles The percentiles P 25, P 50 and P 75 divide the number of data into 4 equal parts, so they are called quartiles. P 25 is also called the lower quartile (denoted by Q 1 ). P 50 is also called the median (denoted by Q 2 ). P 75 is also called the upper quartile (denoted by Q 3 ).

The End