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Lecture 4

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CHEM 212 Lecture 4: Sept. 14/2016
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University of Victoria

Chemistry

CHEM 212

Hamilton M.Coreen

Fall

Description

Chem 212
Lecture 4
Sept. 14/2016
How to use stats controls on calculator:
stats mode
2nd function mode
M+ for adding data points
RCL then xbar and sx
clear= 2nd function CA
Describing the variation in large data sets:
-make the same measurement many time... aka replicates
-Plot the data from measurements you will get normal Gaussian distribution
-+/- 1SD 68% within 1 std. dev of the mean
-16% on either side, tails
-+/- 2 std.dev area is 95.4% within mean
-problem resulting 2 std. dev reports larger range thus less value in number
-95% area is within 2 std.dev
-99% area is within 3 std.dev
-If the data set is large then the data set describes the population
-the average is mu
-std. dev is sigma
-If data set is small then data describes a sample
-the average is xbar
-std. dev is s
* we use xbar and s to predict mu and sigma
-Systematic error does not change to shape of the curve it changes the position along the x-axis
-Eﬀect of change in Precision, Std. dev changes but the mean does not change
-conﬁdence interval aﬀected
-mu and sigma are the true values for the population
-the larger the n, the better the sample estimates the population
-We will measure replicates, calculate xbar and s and use known characteristics of Gaussian distributions to make
conclusions about our data
-We assume that analy

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