CHEM 212 Lecture Notes - Lecture 4: Observational Error, F-TestPremium
2 pages42 viewsFall 2016
SchoolUniversity of Victoria
Course CodeCHEM 212
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How to use stats controls on calculator:!
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 analytical results have random error and apply the concepts from Normal or Gaussian statistics
to interpret our results!
Stating results for an unknown sample !1.
Stating accuracy of results for a known sample!2.
Comparison of 2 data sets:!
Comparison of means t test ( news an F test and then a t test)!1.
Comparison of diﬀerences t test- choice of 2 types of t test!2.
Rejecting a bad data point!
Conﬁdence Interval: Estimate true value from our experimental data!
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