Ch.1 - Intro to General ChemistryWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Standard deviation measures how close our numerical data points are to one another and to the “true” value. 

Mean Value Evaluation

Concept #1: Understanding Standard Deviation


We're going to say that the standard deviation, so standard deviation, measures how close data results are to the mean or average value. We're going to say sometimes it's easy for us to look when we have a few numbers. We just simply look to see how close they are to one another, how close they are to the true value. But sometimes, we may require some help. That's the whole basis for standard deviation.
This is going to become an important idea when it comes to accuracy and precision in this chapter and also when you take your lab. Because when you're doing labs, labs are all based on how accurate and how precise can your measurements be when doing any of the experiments that you have to do.
We're going to say here, the equation for standard deviation is the square root, where we have the summation. This is sigma, the summation of x1 minus x squared divided by n minus one. We're going to say that x or x1 is simply a measurement. We're going to say that x with a bar on top of it is our mean or average of all the measurements added up and divided by the total number of measurements. This is our mean or average. Then we're going to say n, n represents the number of measurements that we have.
The equation might seem a little bit intimidating, but it's really easy as long as you can remember what it is and how do we plug in the numerical values that were given.  

Example #1: Calculate the standard deviation for the following results: 5.29, 5.35 and 5.31.

Practice: Calculate the standard deviation for the following results: 0.039, 0.061 and 5.3 x 10-2