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Question 633:

Roadmarking shall be determined by the retroreflectivity performance of glass beads in the road marking. The roadmarking average level of reflectivity over the City is to be not less than 150 mcd/sqm/lx and the minimum aceptable reflectivity is 120 mcd/m2/lx. Conduct a quarterly assessment of roadmarking condition, randomly sampling 5% of the City Roads each quarter so that 20% of all the roadmarkings are assessed each year. The results shall produce the results specified below. The methods used to perform the assessment shall be sufficient to produce a confidence interval of +/- 5% with a level of confidence of 95%;
(a)Average retroreflectivity for the roadmarking
(b)Percentage of roadmarking that are below the minimum acceptable standard.
The recordings of roadmarkings for the second quarter are as follows:
Reflectivity
226.00
202.00
227.00
245.00
302.00
236.00
277.00
292.00
324.00
350.00
101.00
316.00
252.00
230.00
139.00
145.00
405.00
211.00
249.00
472.00
456.00
334.00
160.00
Please show all workings
Thanks

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