Quiz 1 Solutions

# Quiz 1 Solutions - using correct symbols b Compare the mean...

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STA 3032 Engineering Statistics Quiz 1 Solutions Spring 2011 Problem 1.29 [Page 38]: According to the Society of Civil Engineers, many bridges in the US are either structurally deficient or functionally obsolete. The table below shows the available data from the US Department of Transportation about the conditions of bridges by state as of August 13, 2007. [Assume that we have a SRS of 10 states.] STATES State A L A K F L G A K Y L A M S N C S C T N V A W V % Structurally Deficient (X) 1 2 8 3 7 1 0 1 3 18 13 1 4 7 9 15 % Functionally Obsolete (Y) 1 4 1 5 1 5 13 2 1 1 6 8 16 9 14 17 22 a) WITHOUT USING ANY FORMULA, USING YOUR CALCULATOR ONLY , compute the mean and standard deviation of the percentage of both types of bridges. Write your results
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Unformatted text preview: using correct symbols: b) Compare the mean and the standard deviation and comment on your findings. • The mean percentage of functionally obsolete bridges in the US seems to be more than the mean percentage of structurally deficient bridges. • However, both seem to have the same dispersion around their respective means. • Using the empirical rule, we may state that about 95% of all states have between 2.4% and 19.1% structurally deficient bridges. • Also, by empirical rule we can state that about 95% of the states have between 6.9% ans 23.1% functionally obsolete bridges....
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