Thread: Confidence interval of population mean and true proportion

these 2 questions really has gotten me stumped because there isn't a given standard deviation.. can anyone help me out? here they are...


1)A study found that average time it took a person to find a new job was 5.9 months. If a sample of 36 job seeker was surveyed, find the 95% confidence interval of the population mean. Round your final answer to one decimal.



2)A survey of 80 recent fatal traffic accidents showed that 46 were alcohol-related. Find the 95% confidence interval of the true proportion of fatal alcohol-related accidents. Round our final answer to two decimals.


Thanks in advance.

Originally Posted by infamous

these 2 questions really has gotten me stumped because there isn't a given standard deviation.. can anyone help me out? here they are...


1)A study found that average time it took a person to find a new job was 5.9 months. If a sample of 36 job seeker was surveyed, find the 95% confidence interval of the population mean. Round your final answer to one decimal.



2)A survey of 80 recent fatal traffic accidents showed that 46 were alcohol-related. Find the 95% confidence interval of the true proportion of fatal alcohol-related accidents. Round our final answer to two decimals.


Thanks in advance.

For 2) you would use the binomial distribution in which case you can reasonably approximate the population variance by the sample variance.

For 1) you're probably expected to assume a model for the distribution. At a guess, perhaps the exponential distribution Exponential distribution - Wikipedia, the free encyclopedia

Hi I attach the response as a gif image, hope this helps you