Box Whisker Plot
1. **State the problem:** We need to construct a box-and-whisker plot for the data set: 3, 9, 10, 2, 6, 7, 5, 8, 6, 6, 4, 9, 22, and identify any outliers.
2. **Order the data:** Sort the data from smallest to largest:
$$2, 3, 4, 5, 6, 6, 6, 7, 8, 9, 9, 10, 22$$
3. **Find the median (Q2):** The median is the middle value. There are 13 data points, so the median is the 7th value:
$$Q2 = 6$$
4. **Find the lower quartile (Q1):** The lower half is the first 6 values:
$$2, 3, 4, 5, 6, 6$$
Median of these is average of 3rd and 4th values:
$$Q1 = \frac{4 + 5}{2} = 4.5$$
5. **Find the upper quartile (Q3):** The upper half is the last 6 values:
$$6, 7, 8, 9, 9, 10$$
Median of these is average of 3rd and 4th values:
$$Q3 = \frac{8 + 9}{2} = 8.5$$
6. **Calculate the interquartile range (IQR):**
$$IQR = Q3 - Q1 = 8.5 - 4.5 = 4$$
7. **Determine outlier boundaries:**
- Lower bound: $$Q1 - 1.5 \times IQR = 4.5 - 1.5 \times 4 = 4.5 - 6 = -1.5$$
- Upper bound: $$Q3 + 1.5 \times IQR = 8.5 + 6 = 14.5$$
8. **Identify outliers:** Any data point below -1.5 or above 14.5 is an outlier.
The only value above 14.5 is 22, so 22 is an outlier.
9. **Summary for box plot:**
- Minimum (non-outlier): 2
- Q1: 4.5
- Median: 6
- Q3: 8.5
- Maximum (non-outlier): 10
- Outlier: 22
This completes the box-and-whisker plot construction and outlier identification.