Quantitative Data
Quantitative data are measurements expressed as numbers with units, such as mass in grams or time in seconds.
Definition
Quantitative data are numbers you get by measuring or counting, and they always come with a unit such as centimeters or seconds. They are recorded to the precision of the instrument and can be averaged, graphed, and compared mathematically, which makes them the backbone of analyzing and interpreting results. Values may be continuous (mass, temperature) or discrete counts (seeds germinated), and each carries an uncertainty set by the instrument's resolution and the method. Precision is communicated through significant figures, reliability through repeated trials and measures of spread, and statistical analysis applies only to data of this kind.
Example
Measuring bean plants gives quantitative data: plant A is $8.5\ \text{cm}$ tall, plant B is $7.2\ \text{cm}$, and plant C has $6$ leaves. Timing salt dissolving at three temperatures produces $48\ \text{s}$ at $10^\circ\text{C}$, $26\ \text{s}$ at $30^\circ\text{C}$, and $14\ \text{s}$ at $50^\circ\text{C}$, ready to plot on a line graph. A balance reading $12.47\ \text{g}$ (resolution $0.01\ \text{g}$) and a cylinder reading $5.0\ \text{mL}$ (estimated to $0.1\ \text{mL}$) give a density of $12.47 / 5.0 = 2.494$, reported as $2.5\ \text{g/cm}^3$ because the volume carries only two significant figures.
Key Insight
Think "quantity" for quantitative: a number with a unit. A number without a unit is not data; "the cart went 82" tells nobody anything, while "$82\ \text{cm}$" does. Numbers feel more certain than words, but a measurement is only as good as its instrument and method, and reporting uncertainty alongside the value is what separates quantitative data from a bare number.