In a poll conducted by the Gallup organization in April 2013, 48% of a random sample of 1022 adults in the U.S. responded that they felt that economic growth is more important than protecting the environment. Calculate and interpret a 95% confidence interval for the proportion of all U.S. adults in April 2013 who felt that economic growth is more important than protecting the environment. Make sure to include all steps.

Find a 95% confidence interval for the percentage of stocks with a gain.

In a study designed to determine whether there was a cluster of brain cancer cases at a Pratt & Whitney plant, record from 223,000 employees were studied and 723 employees with brain tumors were found. Treat those employees as a random sample and construct a 95% confidence interval estimate of the proportion of all adults who develop such tumors. write a brief statement interpreting that confidence interval.

Early-childhood-development studies indicate that the more often a child is read to from birth, the earlier the child begins to read. A local parents’ group wants to test this theory and samples families with young children. They find the following results. Construct a 99% confidence interval to estimate the true difference between the proportions of children who read at an early age when they are read to frequently compared to those who were read to less often, as described in the table of results. Let Population 1 be the children who were read to frequently and Population 2 be the children who were read to less often. Round the endpoints of the interval to three decimal places, if necessary.  Ages when Children Begin to Read   Read to at Least Three Times per Week Read to Fewer than Three Times per Week Started Reading by age 4 60 35 Started Reading after age 4 36 51   Lower end point: Upper end point:

A newspaper infographic titled "Social Media Jeopardizing Your Job?" summarized data from a survey of 1,850 recruiters and human resource professionals. The infographic indicated that 52% of the people surveyed had reconsidered a job candidate based on his or her social media profile. Assume that the sample is representative of the population of recruiters and human resource professionals in the United States.   Would a 90% confidence interval be wider or narrower than the 95% confidence interval from part (a)? widernarrower

Suppose NBC has asked the same question to a sample of 1296 adults nine months earlier, finding 47% with an optimistic outlook for the year ahead.  Develop a 95% confidence interval for the percentage of American adults who had an optimistic outlook for the economy nine months earlier.

What effect would increasing sample size have on a confidence interval?  What effect would decreasing sample size have on the margin of error?