(a) A survey found that out of a random sample of 200 workers, 168 said they were interrupted three or more times an hou

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A A Survey Found That Out Of A Random Sample Of 200 Workers 168 Said They Were Interrupted Three Or More Times An Hou 1 (39.13 KiB) Viewed 67 times

(a) A survey found that out of a random sample of 200 workers, 168 said they were interrupted three or more times an hour by phone messages, faxes, etc. Find the 90% confidence interval of the population proportion of workers who are interrupted three or more times an hour. 2.5 Marks (b) The mean life span of population of light bulbs manufactured by Oman electric company is found to be 2400 hours. A sample of 30 light bulbs produced in a lot is found to have a mean life span of 2300 hours with a standard deviation of 250 hours. Test whether the difference between the population and sample means is statistically significant. Assume a = 0.05. 2.5 Marks