3.7 Statistics and Data Interpretation

Why Data Skills Matter

In the TEAS Measurement and Data area you both calculate simple statistics and read information from tables and graphs. Nurses interpret data constantly — trending vital signs, comparing lab values, reading the charts in research articles — so the exam checks whether numbers and pictures translate into correct conclusions. These items are usually quick if you know the four core measures and slow down long enough to read every label on a graph.

Measures of Central Tendency

Central tendency describes the "middle" or typical value of a data set. Three measures appear on the TEAS.

Worked Example: For the data set 3, 5, 7, 7, 9, 10, 12:

• Mean: (3+5+7+7+9+10+12) ÷ 7 = 53 ÷ 7 ≈ 7.57
• Median: the 4th of 7 ordered values → 7
• Mode: 7 (it appears twice)

Finding the Median Correctly

The number-one median mistake is forgetting to order the data first. After ordering:

1. Odd number of values → the single middle number is the median.
2. Even number of values → average the two middle numbers.

Example (even set): 4, 6, 8, 10 has two middle values, 6 and 8, so the median is (6 + 8) ÷ 2 = 7.

Measures of Spread

Spread describes how scattered the data is. The TEAS focuses on the range, the simplest spread measure.

Example: For 2, 4, 6, 8, 10, the range is 10 - 2 = 8. Note that a single extreme outlier pulls the mean toward it but leaves the median relatively stable — which is why median is often the better "typical value" for skewed data.

Reading Graphs and Charts

Each graph type answers a different question, and the TEAS expects you to pick the right reading strategy. Before computing anything, read the title, both axis labels, and the scale.

Worked Example (reading a bar chart): A clinic records patient visits by weekday. Using the bar heights below, the busiest day is the tallest bar (Thursday, 50 visits) and the total for the work week is 30 + 45 + 40 + 50 + 35 = 200 visits. The mean visits per day is 200 ÷ 5 = 40, and the range is 50 - 30 = 20.

Data Trends

A trend is the general direction data moves. On a line graph an upward slope is an increasing trend, a downward slope is decreasing, and a flat line shows no change. Always describe the trend in the variables' own terms ("heart rate rose steadily over six hours"), not just "the line went up."

Correlation Direction

On a scatter plot the cloud of points reveals a relationship called correlation:

• Positive correlation: points trend up from left to right — both variables increase together (e.g., study hours and test scores).
• Negative correlation: points trend down from left to right — one variable rises as the other falls (e.g., absences and grades).
• No correlation: points show no pattern.

Correlation vs. Causation

This is a favorite TEAS reasoning trap. Correlation means two variables move together; causation means one variable actually produces the change in the other. A correlation does not prove causation, because a hidden third factor (a confounder) may drive both.

Real-World Example: Ice-cream sales and drowning deaths both rise in the same months, a strong positive correlation. Ice cream does not cause drowning — hot summer weather independently raises both. On the TEAS, choose answers that say a relationship was observed, not that one thing was proven to cause the other, unless a controlled experiment is described.

Recap

Compute the mean by summing and dividing, the median by ordering and taking the middle (averaging two middles for even sets), the mode by counting frequency, and the range by subtracting min from max. Read every label before interpreting bar, line, pie, and scatter graphs, describe trends in real-world terms, and never upgrade an observed correlation into a claim of causation.