Warren County Telephone Company claims in its annual report that “the typical cu
ID: 3224249 • Letter: W
Question
Warren County Telephone Company claims in its annual report that “the typical customer spends $60 per month on local and long-distance service.” A sample of 12 subscribers revealed the following amounts spent last month.
$64
$65
$63
$66
$60
$63
$69
$60
$65
$60
$53
$67
a.What is the point estimate of the population mean? (Round your answer to 3 decimal places.)
b.Develop a 98% confidence interval for the population mean. (Use t Distribution Table.) (Round your answers to 3 decimal places.)
Warren County Telephone Company claims in its annual report that “the typical customer spends $60 per month on local and long-distance service.” A sample of 12 subscribers revealed the following amounts spent last month.
$64
$65
$63
$66
$60
$63
$69
$60
$65
$60
$53
$67
Explanation / Answer
a.
the point estimate of the population mean=62.9167
b.
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)=62.9167
Standard deviation( sd )=4.231
Sample Size(n)=12
Confidence Interval = [ 62.9167 ± t a/2 ( 4.231/ Sqrt ( 12) ) ]
= [ 62.9167 - 2.718 * (1.221) , 62.9167 + 2.718 * (1.221) ]
= [ 59.597,66.236 ]
c.yes, the company's claim that the typical customer spends $60 per month reasonable
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