Precision (numbers) facts for kids

Precision in mathematics tells us how exact or detailed a number is. It looks at how many digits are shown, especially after a decimal point. For example, if you have the number 54.6, it has one decimal digit, so its precision is 1.

Sometimes, numbers end with zeros. If a number like 500 has two zeros at the end, its precision is -2. A number like 4,000 has three zeros, so its precision is -3. If a whole number does not end in zero, like 7 or 25, its precision is 0.

Precision is different from accuracy. Accuracy means how correct or true a number is when it describes something real. Precision is about the detail of the number itself.

What is Precision?

Precision is about how fine or detailed a measurement or number is. Think of it like drawing a line. A precise line might be drawn with a very sharp pencil. This means you can see many small details. In numbers, precision means showing many digits. This helps us understand how exact a value is.

Digits and Decimal Places

When we talk about precision, we often look at decimal places.

• A number like 3.14 has two decimal places. This means it is quite precise.
• A number like 3.14159 has five decimal places. It is even more precise.

The more decimal places a number has, the higher its precision.

Precision with Whole Numbers

Precision also applies to whole numbers.

• If you measure something as 100 meters, it might mean it's exactly 100 meters. Or it could mean it's somewhere between 99.5 and 100.5 meters.
• If you say 100.0 meters, the ".0" shows more precision. It means the measurement is exact to the first decimal place.

The way a number is written tells us about its precision.

Precision Versus Accuracy

It is easy to confuse precision with accuracy, but they are different.

• Accuracy means how close a measurement or number is to the true or correct value.
• Precision means how close repeated measurements are to each other, or how detailed a single number is.

An Example with Darts

Imagine you are throwing darts at a target.

• If all your darts land very close together, but far from the bullseye, you are precise but not accurate.
• If your darts are spread out but all around the bullseye, you are accurate but not precise.
• If all your darts land very close together and right on the bullseye, you are both accurate and precise.

Why Both Matter

In science and engineering, both accuracy and precision are important.

• You want your measurements to be accurate so they are true.
• You also want them to be precise so they are detailed and reliable.

For example, a scientist measuring a chemical needs both. An inaccurate measurement could lead to wrong results. An imprecise measurement might not be detailed enough.

Why is Precision Important?

Precision is very important in many areas of life and science. It helps us make sure our numbers are useful and reliable.

In Science and Engineering

• When building a bridge, engineers need very precise measurements. Even small errors can cause big problems.
• In chemistry, scientists need to measure chemicals precisely. This ensures experiments work correctly and safely.
• Doctors use precise measurements for medicine doses. This is vital for patient health.

In Everyday Life

• When you bake, precise measurements of ingredients help your recipe turn out right.
• GPS systems use precise calculations to tell you exactly where you are.
• Even in sports, precise timing can decide a winner.

Precision helps us understand the quality of data. It shows us how much we can trust the details of a number.