1-A survey made for the customer satisfaction levels comparison of two competing companies, 174 customers of Company 1 and 355 customers of Company 2 were randomly selected and were asked to rate their companies on a five-point scale, with 1 being least satisfied and 5 most satisfied. The survey results are summarized in the following table: Company 1 vs. Company 2 Sample size=174 | Sample size =355 Mean=3.51 | Mean=3.24 SD=0.51 | SD=0.52 a- Construct a point estimate and a 99% confidence interval for the difference in average satisfaction levels of customers of the two companies. b- Construct a 95% confidence interval for the ratio of the two population variances.
Confidence Interval for Two Population:
1-A survey made for the customer satisfaction levels comparison of two competing
companies, 174 customers of Company 1 and 355 customers of Company 2 were
randomly selected and were asked to rate their companies on a five-point scale, with 1
being least satisfied and 5 most satisfied. The survey results are summarized in the
following table:
Company 1 vs. Company 2
SD=0.51 | SD=0.52
a- Construct a point estimate and a 99% confidence interval for the difference in average
satisfaction levels of customers of the two companies.
b- Construct a 95% confidence interval for the ratio of the two population variances.
2- A gaming business is developing two experimental prototypes for a new computer game.
The first design is put to the test in eleven stores, with a sample standard deviation of twelve
and an average sales of fifty-two. The second design is put to the test in six stores, with a tensample standard deviation and an average of 46 sales. Assume that the two populations are
Make a 95 percent confidence interval for the difference in mean sales between the two
designs.
3- General contractors are granted permission to operate on residential projects by the government.
The government evaluates the project's outcome and assigns a pass or fail grade. If a project fails, it
must be re-evaluated until it succeeds. The department decided to make all contractors' inspection
records available on the internet. It was thought that allowing the public access to the documents
would reduce the number of reinspections. Two samples of records were randomly selected a year
after the web access was made public. Before the web publishing, 500 records were chosen from
the pool, and 200 were chosen afterwards. For each sample, the percentage of projects that passed
the first inspection was recorded. Construct a 90% confidence interval for the difference in the firsttime inspection passing rate between the two time periods.
no public web access -> n1=500 and p1 hat =0.67
public web access -> n2 =100 and p2 hat =0.80
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