Can you please explain also in words, last time they sent me the answer but I did not understand. Thank you Problem: Polychlorinated biphenyls (PCBs) are a group of synthetic oil-like chemicals that...

Can you please explain also in words, last time they sent me the answer but I did not understand.  Thank you

Problem:

Polychlorinated biphenyls (PCBs) are a group of synthetic oil-like chemicals that were at one time widely used as insulation in electrical equipment and were discharged into rivers. They were discovered to be a health hazard, and were banned in the 1970s. Assume that water samples are being drawn from a river in order to estimate the PCB concentration. Suppose that a random sample of size 60 has a sample mean of 1.96 parts per billion (ppb). Assume the population standard deviation is

σ

 = 0.35 ppb.

• 
  Construct a 98% confidence interval for the PCB concentration.
  

• 
  EPA standards require that the PCB concentration in drinking water be no more than 0.5 ppb. Based on the confidence interval, is it reasonable to believe that this water meets the EPA standard for drinking water? Explain.
  

What to do:

• 
  Discrete Probability Distributions
  (If so, in addition to answering word problem: find the mean, variance, and standard deviation. Explain and show work.),


• 
  Normal Distributions
  (If so, in addition to answering word problem: sketch and label the Normal Distribution Curve; sketch and label the standard normal curve; and compute the z-score. Explain and show work.),


• 
  Confidence Intervals
  (If so, in addition to answering word problem: determine the critical value by table or calculator. Explain and show work.),


• 
  Hypothesis Testing
  (If so, in addition to answering word problem: compute the test statistic. Explain and show work.), or


• 
  Correlation/Regression
  (If so, in addition to answering word problem: compute correlation coefficient. Explain and show work.)