Question 635:

Asked on February 22, 2009

Tags: Confidence Intervals , 1-sample t-test

Linemarking for parking bays shall be determined by the retroreflectivity performance of glass beads in the linemarking. The linemarking average level of reflectivity over the City is to be not less than 100 mcd/sqm/lx and the minimum aceptable reflectivity is 80 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:
260.00
263.00
254.00
180.00
174.00
229.00
230.00
56.00
209.00
260.00
309.00
359.00
389.00
491.00
202.00
387.00
440.00
Thanks again

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