QUESTION 1:
Emissions of sulfur dioxide by industry set off chemical changes
in the atmosphere that result in "acid rain." The acidity of
liquids is measured by pH on a scale of 0 to 14. Distilled water
has pH 7.0, and lower pH values indicate acidity. Normal rain is
somewhat acidic, so acid rain is sometimes defined as rainfall with
a pH below 5.0. Suppose that pH measurements of rainfall on
different days in a Canadian forest follow a Normal distribution
with standard deviationσ= 0.5. A sample ofndays finds that the mean
pH isx= 4.8.
Give a 90 % confidence interval for the mean pH μ when n = 5, n = 15, and n = 40.
n= 5 to
n = 15 to
n = 40 to
QUESTION 2:
A survey of licensed drivers inquired about running red lights. One question asked, "Of every ten motorists who run a red light, about how many do you think will be caught?" The mean result for 816 respondents was x¯¯¯x¯ = 1.93 and the standard deviation was s = 2.02. For this large sample, s will be close to the population standard deviation s, so suppose we know that s = 2.02.
Give a 95% confidence interval (±0.01) for the mean opinion in the population of all licensed drivers: ± .
The distribution of responses is skewed to the right rather than Normal. Will it strongly affect the z confidence interval for this sample?



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