©G Dear 2010 – Not to be sold/Free to use Displaying Single Data Sets Applied Mathematic (Preliminary General 1) Percentiles, Deciles & Quartiles Stage 6 - Year 11 Press Ctrl-A ©G Dear 2010 – Not to be sold/Free to use

*Percentiles, Deciles and Quartiles What’s all this about? We want to know the spread of the scores. The 20th percentile is the score that has 20% of the scores below it. It is also known as the 2nd decile. End of Slide

*Percentiles, Deciles and Quartiles What’s all this about? We want to know the spread of the scores. The 25th percentile is the score that has 25% of the scores below it. It is also known as the lower quartile or Q1. End of Slide

*Percentiles, Deciles and Quartiles What’s all this about? We want to know the spread of the scores. The 75th percentile is the score that has 25% of the scores below it. It is also known as the upper quartile or Q3. End of Slide

*Percentiles, Deciles and Quartiles What’s all this about? What’s the spread of the scores. The 50th percentile is the score that has 50% of the scores below it. It is also known as the 5th decile or median . End of Slide

The spread of the middle 50% of scores. Interquartile Range The spread of the middle 50% of scores. IQR = Q3 – Q1 Q3 = 75th percentile = 12 Median = 50th percentile = 11 (5th decile) Q1 = 25th percentile = 10 IQR = 12 - 10 = 2 Small IQR 2 4 6 8 10 12 14 16 18 20 End of Slide

The spread of the middle 50% of scores. Interquartile Range The spread of the middle 50% of scores. IQR = Q3 – Q1 Q3 = 75th percentile = 13 Median = 50th percentile = 11 (5th decile) Q1 = 25th percentile = 7 IQR = 13 - 7 = 6 Medium IQR 2 4 6 8 10 12 14 16 18 20 End of Slide

The spread of the middle 50% of scores. Interquartile Range The spread of the middle 50% of scores. IQR = Q3 – Q1 Q3 = 75th percentile = 18 Median = 50th percentile = 11 (5th decile) Q1 = 25th percentile = 3 IQR = 18 - 3 = 15 Large IQR 2 4 6 8 10 12 14 16 18 20 End of Show