## Lesson 5: Variance

September 6, 2015

**Mon Sep 7**

Review:

- Central Tendency
- Week 1 slides

Presentation:

- Variance
- Percentiles and Quartiles
- Position in data set = i = percentile * n
- 50th Percentile = Median
- Q1 = 25th Percentile
- Q2 = 50th Percentile = Median
- Q3 = 75th Percentile
- Interquartile Range (IQR = Q3 – Q1)

**Box Plots: video**- Visualize variance

**Standard Deviation: video**- Calculate variance

- Example
- Data: {213, 345, 609, 73, 167, 243, 444, 524, 199, 682}
- Calculate Q1, Q2, Q3, IQR
- Calculate standard deviation

- Percentiles and Quartiles

Activity:

- Use Data set 1 and 2 below
- Data set 1: {2, 4, 8, 4, 6, 2, 7, 8, 4, 3, 8, 9, 4, 3, 5}
- Data set 2: {7, -2, 5, 9, 0, -3, -6, -7, -4, -5, 2, -8}

- Calculate the following
- Q1, Q2, Q3, IQR for each data set, separately
- Draw Box Plots side by side for comparison
- Calculate mean and standard variation, separately

Assignment:

- Using Sheets and the D60-D70 % Free-Reduced Lunch data
- Calculate Q1, Q2, Q3 and IQR (for D60 and D70, separately)
- Draw Box Plots side by side for comparison
- Calculate standard variation