Question

An ecological group suspects lobsters are consuming dangerous levels of mercury in a region of the world. Dangerous levels of mercury are classified when they reach beyond 6.5 parts per million. A random sample of 25 lobsters in the region were tested and the data is shown in the stemplot.
Stemplot for Mercury Levels.
2|2 4;
2|;
3|1 4;
3|5 8;
4|0 2;
4|5 6;
5|0 1 3 3 4;
5|6 8 9;
6|3 4;
6|6 7 8;
7|1 2;
7|

Key: 2|2 = 2.2 parts per million

Part A: What proportion of the lobsters in the sample have dangerous levels of mercury in their systems? (4 points)

Part B: Construct and interpret a 95% confidence interval for the mean mercury levels of the lobsters if the sample of 25 lobsters has a mean mercury level of 5.05 parts per million and standard deviation of 1.45 parts per million. (6 points)

Answer 1

Part A: 5 out 25 lobsters have dangerous levels of mercury

Part B: the 95% confidence interval is given by (4.45, 5.65)

since everything is given all I had to do is find the critical value which can be found from the resource packet = 2.064

Using the formula we find 5.05+-2.064*1.45/5 = ( 4.45,5.65)

For this case, we have 95% of confidence that the true mean for the average number of lobsters with dangerous levels of mercury is between 4.45,5.65