Fish from a lake have the following mercury content: 1.80ppm, 1.58ppm, 1.64ppm. previous analysis show σ=0.10. what is the 90% confidence interval (+- of the second result?

2) fish from a lake have the following mercury content: 1.80ppm, 1.58ppm, 1.64ppm. previous analysis show σ=0.10. what is the 90% confidence interval (+- of the sample mean?

3) the carbon in a steel sample was measured as (%w/w): 2.0%, 2.5%, 2.1%, and 1.9%. if s=0.26%, what is the 95% confidence interval of the mean (+-

4) a class of 30 students found the average ph of a standard sample to be 7.00 with a standard deviation of 0.15. the accepted true value of the standard is ph = 7.10. can we say with 95% confidence level that the measurements agree with the sandard?

5) an analytical chemist developed a new method to measure ca in milk and used it to test a standard reference material milk sample known to have 2.0mm ca. the results were 1.50, 1.80, 1.90, and 1.90mm (s=0.19). is there a bias in the new method at 95% confidence level?

6) you would like to know if the beer from a glass has the same alchohol content to an open bottle in the vicinity. five measurements of the glass gave an average of 4.55% ethanol. six measurements of the bottle gave an average of 4.50% ethanol. the pooled s = 0.080%. is there a difference in the alcohol content at the 95% confidence level?