Apply Probability and Statistics in Scientific Contexts

Science is built on observation, but observations can be messy. Two patients might respond differently to the same medicine. Two weather stations might record different temperatures on the same day. Probability and statistics give scientists the tools to cut through that messiness, find real patterns, and make confident conclusions. Without these tools, we would have no way to tell whether a new drug actually works or whether a crop really grows better with a certain fertilizer.

On the GED Science test, you will not be asked to perform complex statistical calculations. Instead, you will be asked to interpret data presented in tables, graphs, and passages — and to use basic ideas like averages, ranges, and probability to evaluate scientific claims. The big question this lesson addresses is: How do you look at a set of numbers and figure out what they are really telling you?

Before we dive into calculations, let's establish the key ideas you will encounter on the GED. These concepts appear again and again, whether the topic is biology, chemistry, earth science, or physics.

The diagram below shows the daily high temperatures recorded over one week at a weather station. It illustrates how we calculate the mean, median, and range from those seven data points.

Notice how the mean and median are close together here. That happens when data are fairly symmetrical. If Sunday's temperature had been 40 °F instead of 65 °F (an extreme outlier), the mean would drop significantly, but the median would barely change. This is why scientists often report both values — the median resists being pulled by outliers.

The GED provides an on-screen calculator (TI-30XS), so you will not need to do heavy arithmetic by hand. However, understanding the formulas helps you know what the numbers mean and when to apply each one.

Probability shows up across every branch of science. In genetics, we predict the likelihood that offspring will inherit a particular trait. In earth science, we discuss the probability of earthquakes or severe storms. In medicine, we evaluate how likely a treatment is to succeed. The diagram below shows one of the most common probability tools in biology: a Punnett square.

On the GED, you might see a Punnett square and be asked: "What is the probability that offspring will have blue eyes?" The answer is found by counting favorable outcomes (1 out of 4 cells shows bb) and dividing by total outcomes (4). That gives 1/4 = 0.25 = 25%. Probability questions in other contexts — such as "What is the chance that a volcano will erupt in the next 50 years?" — follow the same logic of favorable outcomes divided by total outcomes, though the data source may be historical records rather than a genetic model.

Let's walk through a GED-style scenario step by step. Read the passage and data table below, then follow the analysis.

Statistical tools are powerful, but they can be misused or misunderstood. On the GED, you may be asked to identify weaknesses in a study or explain why a conclusion is not fully supported. The table below summarizes what each statistical measure does well and where it falls short.

The GED Science test does not ask you to perform advanced statistical tests, but it does expect you to understand the ideas behind them. In professional science, researchers go beyond means and ranges to use tools like standard deviation and statistical significance. Here is a quick comparison of what you need for the GED versus what scientists use in the field.

The takeaway here is that the GED tests your foundational understanding — whether you can read a table, compute a basic statistic, and use it to evaluate a scientific claim. If you master the concepts in this lesson, you will have a strong base not only for the test, but for any future coursework in science, health, or social science.