SOLUTION: A travel agency call Centre wants to know the average of calls received by its call Centre. A random sample of 21 days is selected and the sample mean number of calls received was

Question 1145329: A travel agency call Centre wants to know the average of calls received by its call Centre. A random sample of 21 days is selected and the sample mean number of calls received was found to be 166.2 with a sample standard deviation of 22.8 calls. Assume that calls received daily are normally distributed.
Find the 99% confidence interval for the mean number of daily calls received by the call Centre.
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
alpha(a) = 1 - (99/100) = 0.01
:
critical probability(p*) = 1 - (a/2) = 0.995
:
since the sample(21 days) < 30 and the population standard deviation is unknown, we find the critical value(CV) using the t statistic
:
degrees of freedom(DF) = 21 - 1 = 20
:
Using p* and DF, the CV is 2.845
:
standard error(SE) = sample standard deviation/square root(sample size) = 22.8/square root(21) = 4.975
:
Margin of Error(ME) = CV * SE = 2.845 * 4.975 = 14.15 is approximately 14.2
:
The 99% confidence interval for the mean number of daily calls received by the call Centre is 162.2 + or - 14.2 or (176.4, 148)
:
RELATED QUESTIONS
A travel agency call centre wants to know the average number of calls received per day... (answered by CPhill)

QUESTION 2 2.1 What determines use of t-distribution and z-distribution in... (answered by ikleyn)

2.1 What determines use of t-distribution and z-distribution in confidence interval... (answered by ikleyn)

A call centre receives 20 call per hour on an average. Should the centre be employing... (answered by mathmate)

In a single week at a Call Centre, the team of Jimmy, Stephanie, Tom and Abigail had... (answered by josgarithmetic)

``In a single week at a Call Centre, the team of Jimmy, Stephanie, Tom and Abigail had... (answered by josgarithmetic)