# Ruler of All

Ruler of All

Michelle Whang

Partner: Cecilia An

Date Done: September 21, 2007

Date Turned In: September 28, 2007

Purpose

The purpose of this lab was to verify the certainty of a range of measuring devices, and to correctly establish the number of significant figures to record the measurements as well as to calculate them.

Experimental Procedure

See the attached experiment.

Data

See the attached data.

Theoretical Section/Discussion of Results

Everybody makes and utilizes measurements on a daily basis. Scientists, not excluding, make and use measurements, because it is fundamental to their data. Measurement is how much there is of something that you can quantify. Measurements include a number and unit.

All measuring instruments are susceptible to a certain amount of uncertainty. Uncertainty is accounted by instrument design and can be best defined as the degree of variability in the observations. In a measurement, estimation is always done to one more place value than what is already calibrated on the instrument. Usually, the more calibrated it is, the more numbers an instrument will allow to be recorded, which means the more certain the value is.

In every lab, it is every scientist’s goal to generate measurements that are both correct and reproducible.  Being correct and able to reproduce similar measurements can be related through the concepts of accuracy and precision. Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured. To calculate the accuracy of a measurement you need to compare the result to a true value. Usually, the more numbers that are able to show, it may also mean an increase in accuracy. Precision is a measure of how close a series of measurements are to one another.  To see how precise a measurement is, you must compare the value to two or more repeated measurements. It is possible to determine the precision of a measurement without a true value, unlike accuracy, because precision is based on how close together the results are, regardless of the correct value. Precision has no direct relation with certainty or accuracy, but just like accuracy, the more numbers that can be read, a greater precision the measurement will hold.

The system of significant figures plays an important role in the uncertainty of measurements. Significant figures in a measurement comprise of all known digits, plus a last digit that is estimated. Essentially, the more significant figures in a value, the less uncertainty there is. It is vital that all calculations be recorded with the correct number of significant figures, because the answers often depend on the number of significant figures in the values used in the calculations. For this reason, there are several rules everyone must follow when utilizing significant figures:

First, all nonzero integers are always considered ...