Determining confidence interval for mean ph in rainfall

Reference no: EM1315357

Q1) Acid Rain, caused by reaction of certain air pollutants with rainwater, appears to be growing problem in northeastern United States. (Acid rain affects soil and causes corrosion on exposed metal surfaces.) Pure rain falling through clean air registers pH value of 5.7 (pH is a measure of acidity: 0 is acid; 14 is alkaline). Assume water samples from 40 rainfalls are analyzed for pH, and x and s are equal to 3.7 and .5, respectively.

i) Determine a 99% confidence interval for mean pH in rainfall. How would you distinguish interval?

ii) What supposition should be made for confidence interval to be valid?

Q2) The mean cleanup and redecorating time for a one-bedroom student apartment at campus Housing is 16 hours. Time for cleanup and redecorating process follows normal distribution. Campus Housing administration instituted a "fee and fine system" which encourages students to clean their apartments when they vacate them. This must shorten cleanup and redecorating time. Sample of 15 apartments had mean cleanup and redecorating time of 14.5 hours with standard deviation of 1.5 hours. Does use of "fee and fine system" decrease cleanup and redecorating time? Follow 5-step hypothesis testing procedure using 0.05 significance level.

a) Define the null and alternate hypotheses.

b) What is the level of significance?

c) Calculate the value of the test statistic.

d) Formulate the decision rule.

e) What is your decision regarding null hypothesis? Interpret result.

Reference no: EM1315357

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