This document discusses key concepts related to accuracy in measurements. It defines error as the difference between the real and observed value of a measurement. Accuracy is the closeness of a measured value to the actual value, illustrated by measuring a pencil's length. Precision refers to the closeness of multiple measurements to each other. The document also covers approximation, which is finding a number close to an exact measurement value, and rounding off numbers based on defined rules.

3. Measurements is the base of
all experiments in science
and technology.
ACCURACY IN MEASUREMENTS

4. The value of every
measurement contains
some uncertainty. These
certainties are called
‘ERRORS’

5. ERROR: The difference between the real value and the observed value is called
an error.
Example:
Length of your pencil is 5.2 cm, but you measure it as 4.5cm. Then it is an error.
Here real value is 4.5cm and observed value is 4.5 cm.
The error is 0.7mm
5.2cm
Real value =5.2cm
Observed value= 4.5cm
Error = 0.7mm

6. ACCURACY:
Now, you measure the same pencil
as 5.1cm. It is closed to the real value
5.2cm. So, we can say it is an accurate
value.
Accuracy is the closeness of a
measured value to the actual value or
true value.

7. Precision: you are measuring the pencil 3 times and the
measurements are 5.1cm, 5.2cm, and 5.3cm. The
measured values are close to each other. This is precision.
Precision is the closeness of two or more
measurements to each other.
5.1cm 5.2cm 5.3cm

8. APPROXIMATION:
Your mother is cooking at home. While
preparing the dish the ingredients like
pepper, salt, garlic, etc., are taken
approximately.
Approximation is the process of finding
a number, which is acceptably close to exact
value of measurement of a physical quantity.

9. ROUNDING OFF:
Calculators are widely used in day-
to-day life to do calculations. The
result given by a calculator has too
many digits. Hence, the result
containing more digits should be
rounded off.

10. RULES OF ROUNDING OFF:
1. Decide which is the last digit to keep.
2. Leave it the same, id the next digit is less than 5
For Example:
If we round off the number 2.634 to two decimal
places. The answer is 2.63.

11. 3. Increase it by one, if the next digit is 5 or greater
than 5.
For Example:
If we round off the number 1.8686 to three decimal
places the answer is 1.869.

12. 1. Define error.
2. What is accuracy?
3. Define precision?
4. Round off the number 1.864 to two decimal
places.
ASSIGNMENT