Key Takeaways
- Mean = sum ÷ count; Median = middle value (order first); Mode = most frequent
- For even data sets, the median is the average of the two middle numbers
- Range = Maximum - Minimum value
- Positive correlation: both variables increase together; negative: one increases as other decreases
- Probability = favorable outcomes ÷ total possible outcomes
Statistics and Data Interpretation
The TEAS tests your ability to calculate basic statistics and interpret data from tables, graphs, and charts—essential skills for understanding patient data and research.
Measures of Central Tendency
Central tendency describes the "center" of a data set.
| Measure | Definition | How to Calculate |
|---|---|---|
| Mean | Average | Sum of values ÷ number of values |
| Median | Middle value | Middle number when data is ordered |
| Mode | Most frequent | Value that appears most often |
Example Data Set: 3, 5, 7, 7, 9, 10, 12
- Mean: (3+5+7+7+9+10+12) ÷ 7 = 53 ÷ 7 = 7.57
- Median: 7 (4th value of 7 ordered numbers)
- Mode: 7 (appears twice)
Finding the Median
Odd number of values: The middle number Even number of values: Average of the two middle numbers
Example: 4, 6, 8, 10
- Two middle values: 6 and 8
- Median = (6 + 8) ÷ 2 = 7
Measures of Spread
| Measure | Definition | How to Calculate |
|---|---|---|
| Range | Spread of data | Maximum - Minimum |
| Variance | Average squared deviation | Σ(x - mean)² ÷ n |
| Standard Deviation | Typical deviation from mean | √Variance |
Example: Data set: 2, 4, 6, 8, 10
- Range: 10 - 2 = 8
Percentiles and Quartiles
Percentile: The percentage of values below a given value.
- 75th percentile means 75% of values are below this score
Quartiles: Divide data into four equal parts
- Q1 (25th percentile)
- Q2 (50th percentile = median)
- Q3 (75th percentile)
- IQR (Interquartile Range) = Q3 - Q1
Reading Tables
Tips for Tables:
- Read the title first
- Identify what rows and columns represent
- Look for trends or patterns
- Pay attention to units
| Year | Hospital A Admissions | Hospital B Admissions |
|---|---|---|
| 2023 | 5,200 | 4,800 |
| 2024 | 5,500 | 5,100 |
| 2025 | 5,800 | 5,400 |
Interpretation: Both hospitals show increasing admissions, with Hospital A consistently higher.
Reading Graphs
Bar Graphs: Compare categories
- Look at bar heights
- Compare differences between bars
Line Graphs: Show trends over time
- Look for increasing/decreasing patterns
- Identify peaks and valleys
Pie Charts: Show parts of a whole
- Each slice is a percentage
- All slices total 100%
Scatter Plots: Show relationships between variables
- Positive correlation: points trend upward
- Negative correlation: points trend downward
- No correlation: random scatter
Calculating from Graphs
Reading values: Find the point, trace to the axis Calculating change: New value - Old value Calculating percent change: (Change ÷ Original) × 100
Probability Basics
Probability = Number of favorable outcomes ÷ Total possible outcomes
Example: What is the probability of rolling a 4 on a die?
- Favorable: 1 (just the 4)
- Total: 6 (numbers 1-6)
- Probability: 1/6 ≈ 0.167 ≈ 16.7%
Probability Rules
| Type | Formula | Example |
|---|---|---|
| And (both events) | P(A) × P(B) | Flip 2 heads: 1/2 × 1/2 = 1/4 |
| Or (either event) | P(A) + P(B) - P(A and B) | Roll 2 or 4: 1/6 + 1/6 = 2/6 |
| Complement | 1 - P(event) | Not rolling 6: 1 - 1/6 = 5/6 |
Healthcare Statistics Applications
| Application | Statistical Measure |
|---|---|
| Average blood pressure | Mean |
| Typical patient age | Median |
| Most common diagnosis | Mode |
| Lab value normal range | Mean ± 2 standard deviations |
| Treatment success rate | Percentage/Probability |
Find the median of: 12, 5, 8, 3, 15, 9, 7
A data set has values: 4, 4, 5, 6, 6, 6, 8, 9. What is the mode?
In a scatter plot showing the relationship between hours of study and test scores, the points trend upward from left to right. This indicates: