# Null Hypothesis Waterbody - Environmental Statistics

1. Apr 5, 2013

### joemama69

1. The problem statement, all variables and given/known data

Past study in a contaminated waterbody has revealed that the percentage contamination level of the surface water has been determined at 24.75%

a)Based on a study of a random sample of 40 containers of the same size, it is observed that the sample percentage of contaminted containers is 21.65%. Does it indicate that some efforts have gone into cleaning of the waterbody?

b)An independant organization conducted a similar parallel study at it revealed that the percentage contaminatin level was 22.78% based on a sample size of 25. Does this corroborate the decision reached in question A.

c)Can you combine the two data sets and come up with a bettter understanding about the level of contamination of the waterbody.

2. Relevant equations

I believe we use P +/- 1.645 sqrt((P(1-P)/n) with a confidence level of 95%

3. The attempt at a solution

See attached pdf . Does anyone see any issues with my calculations? Just realized my 95% CI z value should be 1.645 not 1.654. Other than that, any issues?

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