Scientific Measurements

Accuracy and Sensitivity of Measuring Devices

Accuracy 

- It is the degree of closeness of the measurements to the actual or true value.
- The extent to which a given measurement agrees with the standard value for that measurement.


Sensitivity

- It measures the proportion of actual positives which are correctly identified.

- An ability to differentiate fluctuations in a given observed or tested event.

Getting the Accuracy and the Sensitivity

- After getting the Accuracy it will be easier to get the sensitivity.

Getting the Accuracy

- It  is how close the measured values are to each other.

NOTE: Accuracy depends on the instrument you are measuring with. But as a general rule: The degree of accuracy is half a unit each side of the unit of measure.

Getting the Sensitivity

- In getting the sensitivity it is the next calibration to the accuracy. But it is not represented by a line on the measuring tool.

- In other words, it is the next place value after your accuracy. Or sometimes, it depends on the picture.

Example:

The accuracy from this ruler is 

TENTHS.

The sensitivity is HUDREDTHS.

Accuracy and Precision

- Accuracy is the degree of veracity while precision is the degree of reproducibility.

Precision

- It is a system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.

NOTE: 
- A measurement system can be accurate but not precise, precise but not accurate, neither, or both.

• Good precision simply tells how well a series of measurements cluster around the average result. The precision is good in Figure 3 and Figure 4. The precision is poor in Figure 1 and Figure 2.

• Figure 1 and Figure 3 shows good accuracy. If the average value is close to the middle, then we have good accuracy. We can have good accuracy even when the precision is poor.

Bias is a systematic (built in) error which makes all measurements wrong by a certain amount.

Examples!

How To Compute For Percentage Error
- The calculation for percentage error is used to evaluate the degree of error in calculations and data.

- The calculation for percentage error is simple and straightforward. 

FORMULA FOR PERCENTAGE ERROR:

Example on how to do Percentage Error!

A student measures the mass and volume of a piece of copper in the laboratory and uses his data to calculate the density o the metal.  According to his results, the copper has a density of 8.37 g/cm³.   Curious about the accuracy of his results, the student consults a reference table and finds that the accepted value for the density of copper is 8.92 g/cm³.   What would be the student's percent error?

Step 1 - Determine which values are known.
                       The students result, or the observed value = 8.37 g/cm³.
                       The accepted, or true value = 8.92 g/cm³.

Step 2 - Substitute the values in the percent error calculation.

Step 3 - Solve for the unknown, and round to correct significant digits.

Percentage Error = -6.17%

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Group 3

Mendoza

Trillanes

Meily

Manibog

Macomb