Consumption of alcoholic beverages by young women of drinking age in the United

Question

Consumption of alcoholic beverages by young women of drinking age in the United Kingdom, the United States, and Europe was reported (The Wall Street Journal, February 15, 2006). Data (annual consumption in liters) consistent with the findings reported in The Wall Street Journal article are shown for a sample of 20 European young women.

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Assuming the population is roughly symmetric, construct a 95% confidence interval for the mean annual consumption of alcoholic beverages by European young women. Round your answers to two decimal places.
  to  liters per year.

Explanation / Answer

Getting the mean and standard deviation,

X = 128.2
s = 64.97416491

Note that              
              
Lower Bound = X - t(alpha/2) * s / sqrt(n)              
Upper Bound = X + t(alpha/2) * s / sqrt(n)              
              
where              
alpha/2 = (1 - confidence level)/2 =    0.025          
X = sample mean =    128.2          
t(alpha/2) = critical t for the confidence interval =    2.093024054          
s = sample standard deviation =    64.97416491          
n = sample size =    20          
df = n - 1 =    19          
Thus,              
              
Lower bound =    97.79115478          
Upper bound =    158.6088452          
              
Thus, the confidence interval is              
              
(   97.79115478   ,   158.6088452   ) [ANSWER]

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