The Packaging Company sells soda and claims each can contain

The Packaging Company sells soda and claims each can contains 12 oz. A random sample of 15 soda yielded a sample mean of 11.2 oz. Given the sample standard deviation is 0.3 oz, give a 90% confidence interval. Give lower limit and upper limit accurate to two decimals; that is, 12.345 would be entered 12.35.

Solution

Confidence Interval
CI = x ± t a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
ta/2 = t-table value
CI = Confidence Interval
Mean(x)=11.2
Standard deviation( sd )=0.3
Sample Size(n)=15
Confidence Interval = [ 11.2 ± t a/2 ( 0.3/ Sqrt ( 15) ) ]
= [ 11.2 - 1.761 * (0.08) , 11.2 + 1.761 * (0.08) ]
= [ 11.06,11.34 ]