HOME

Course Chapters

Mathematics Review

Basic Concepts

Advanced Concepts

Section Tests

Pre-test

Post-test

Useful Materials

Glossary

Links

Texas Instruments Calculators

Casio Calculators

Sharp Calculators

Hewlett Packard Calculators

Calculators

Units Conversion Lookup

Nomenclature

Redox

Kinetics

Thermo

Nuclear

Linear Least Squares Regression

Newton's Method Equation Solver

Gas Laws

Credits

Contact Webmaster

Simple Statistics

A student analyzing a sample for bromine (Br) makes four trials with the following results: 36.0, 36.3, 35.8, and 36.3. The theoretical value is 36.2

Calculate:

  1. the arithmetic mean
  2. the percent error for each trial
  3. the deviation and percent deviation for each trial
  4. the standard deviation

Arithmetic mean:

(36.0 + 36.3 + 35.8 + 36.3) / 4 = 36.1

Percent error, deviation and percent deviation for each trial

Observed value Error Percent error Deviation Percent deviation
36.0 -0.2 0.55% -0.1 -0.28%
36.3 0.1 0.28% 0.2 0.55%
35.8 -0.4 1.1% -0.3 -0.83%
36.3 0.1 0.28% 0.2 0.55%

Standard deviation

Trial 1 2 3 4
Percentage of Br 36.0 36.3 35.8 36.3
d -0.1 0.2 -0.3 0.2
d2 0.01 0.04 0.09 0.04

Adding up all of the d2= 0.18
Dividing 0.18 by 3 (or 4-1) = 0.06
Taking the square root of 0.06= 0.245

Back to Statistics Main Page

Developed by
Shodor
in cooperation with the Department of Chemistry,
The University of North Carolina at Chapel Hill

Copyright © 1996-2008 Shodor
Please direct questions and comments about this page to
[email protected]