In science, “DV” most commonly stands for dependent variable, the thing you measure in an experiment to see whether it changed. You’ll also see “DV” in nutrition science, where it stands for Daily Value, the reference amount of a nutrient listed on food labels. Both meanings come up frequently in science classes, so here’s what each one means and how it works.
Dependent Variable: The Outcome You Measure
A dependent variable is the outcome in an experiment. It’s called “dependent” because its value depends on what you change during the experiment. The thing you deliberately change is the independent variable (IV), and the dependent variable (DV) is what responds to that change.
A simple way to remember it: the independent variable is what you do, and the dependent variable is what happens as a result. If you’re testing whether fertilizer helps plants grow taller, the amount of fertilizer is the independent variable and plant height is the dependent variable. You measure the DV to find out whether your experiment had any effect.
How To Spot the DV in a Hypothesis
In any hypothesis, the dependent variable is the outcome being predicted. Consider this example from the National Library of Medicine: researchers wanted to know whether high concentrations of vehicle exhaust affect asthma rates in children. The concentration of exhaust is the independent variable (the thing that differs between groups), and asthma incidence is the dependent variable (the outcome being tracked).
Another example: studying whether birth order is linked to Down syndrome prevalence. Birth order is the independent variable, and the prevalence of Down syndrome is the dependent variable, because it’s the measurement that changes in response to different birth orders.
To identify the DV in any experiment, ask yourself: “What am I measuring at the end?” That’s your dependent variable. You cannot have a dependent variable without an independent variable, because the whole point of a DV is that it responds to something else.
DVs Across Different Sciences
Dependent variables show up in every scientific field, but what you measure looks different depending on the discipline:
- Biology: growth rate of bacteria, heart rate, number of offspring, enzyme activity
- Chemistry: reaction rate, temperature change, mass of product formed, color change
- Physics: distance traveled, time elapsed, voltage, acceleration
- Psychology: test scores, reaction time, self-reported anxiety levels
In each case, the DV is whatever gets recorded in your data table after you run the experiment.
An Important Nuance: Association vs. Cause
It’s tempting to say the independent variable “causes” changes in the dependent variable, but that’s not always accurate. A more precise way to describe it: the independent variable is associated with variations in the dependent variable. True cause-and-effect can only be established in well-controlled experiments. In observational studies (where researchers watch what happens without manipulating anything), the DV still changes alongside the IV, but you can’t be sure the IV is the reason why.
DV in Nutrition: Daily Value
If you encountered “DV” on a food label or in a nutrition class, it stands for Daily Value. The FDA developed Daily Values as reference amounts for nutrients, expressed in grams, milligrams, or micrograms, representing how much of a given nutrient you should consume (or not exceed) each day.
On a Nutrition Facts label, you’ll see “%DV” next to each nutrient. This tells you what percentage of your total daily need is covered by one serving of that food. The FDA offers a quick rule of thumb: 5% DV or less per serving is considered low, and 20% DV or more per serving is considered high. So if a cereal lists 25% DV for iron, one bowl gives you a quarter of the iron you need for the day.
Daily Value vs. Recommended Dietary Allowance
Daily Values are not the same thing as Recommended Dietary Allowances (RDAs), though they’re related. RDAs vary by age and sex. A teenage boy needs different amounts of certain vitamins than a 60-year-old woman. But food labels can’t print a different number for every demographic, so the FDA picks a single reference number for each nutrient. That single number is the DV. It’s often close to the RDA for most adults, but not always an exact match.
The nutrients the FDA specifically encourages you to get more of include dietary fiber, vitamin D, calcium, iron, and potassium. The ones to keep low: saturated fat, sodium, and added sugars. Using the 5%/20% guideline makes it easy to compare products at a glance without doing any math.