Are Florida Lakes Acidic or Alkaline? The pH of a liquid is a measure of its acidity or alkalinity. Pure water has a pH of 7, which is neutral. Solutions with a pH less than 7 are acidic while solutions with a pH greater than 7 are basic, or alkaline. The dataset FloridaLakes gives information, including pH values, for a sample of lakes in Florida. Computer output of descriptive statistics for the pH variable is shown: Descriptive Statistics: pH Variable N N* Mean SE Mean StDev Minimum Q1 Median Q3 Maximum pH 53 0 6.591 0.177 1.288 3.600 5.800 6.800 7.450 9.100 (a) How many lakes are included in the dataset? What is the mean pH value? What is the standard deviation? Enter the exact answers. n= x¯= s= (b) Use the descriptive statistics above to conduct a hypothesis test to determine whether there is evidence that average pH in Florida lakes is different from the neutral value of 7. State the null and alternative hypotheses. (c) Show all details of the test described in part (b) and use a 5% significance level. Give the test statistic and the p-value. Round your answer for the test statistic to two decimal places and your answer for the p-value to three decimal places. test statistic= p-value= What is the conclusion? _______________ H0. If there is evidence that it is not neutral, does the mean appear to be more acidic or more alkaline? (d) Compare the test statistic and p-value you found in part (c) to the computer output below for the same data: One-Sample T: pH Test of mu =7 vs not =7 Variable N Mean StDev SE mean 95% CI T P pH 53 6.591 1.288 0.177 (6.235,6.946) -2.31 0.025 o The same up to round off error o Different
Are Florida Lakes Acidic or Alkaline? The pH of a liquid is a measure of its acidity or alkalinity. Pure water has a pH of 7, which is neutral. Solutions with a pH less than 7 are acidic while solutions with a pH greater than 7 are basic, or alkaline. The dataset FloridaLakes gives information, including pH values, for a sample of lakes in Florida. Computer output of
Descriptive Statistics: pH
Variable N N*
pH 53 0 6.591 0.177 1.288 3.600 5.800 6.800 7.450 9.100
(a) How many lakes are included in the dataset? What is the mean pH value? What is the standard deviation? Enter the exact answers.
n=
x¯=
s=
(b) Use the descriptive statistics above to conduct a hypothesis test to determine whether there is evidence that average pH in Florida lakes is different from the neutral value of 7.
State the null and alternative hypotheses.
(c) Show all details of the test described in part (b) and use a 5% significance level.
Give the test statistic and the p-value. Round your answer for the test statistic to two decimal places and your answer for the p-value to three decimal places.
test statistic=
p-value=
What is the conclusion? _______________ H0.
If there is evidence that it is not neutral, does the mean appear to be more acidic or more alkaline?
(d) Compare the test statistic and p-value you found in part (c) to the computer output below for the same data:
One-Sample T: pH
Test of mu =7 vs not =7
Variable N Mean StDev SE mean 95% CI T P
pH 53 6.591 1.288 0.177 (6.235,6.946) -2.31 0.025
o The same up to round off error
o Different
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