Question

Airline Reservations Waiting Time: When customers phone an airline to make reservations, they usually find it irritating if they are kept on hold for a long time. In an effort to determine how long phone customers are kept on hold, one airline took a preliminary random sample of 167 phone calls and determined the average length of time (in minutes each caller was kept on hold). The sample standard deviation was 3.8 minutes. To estimate the true population mean hold times, the researcher wants to use a 95% confidence level. 1) What is the critical value for the 95% confidence level? Critical value z_c= 1.96 (round answer to 2 decimal places) 2) Please answer three parts a,b,c below to figure out: How many more customers should be included in the sample in order to be 95% sure that the sample mean of holding times is within one-half of a minute of the population mean hold times? a) The margin of Error E= 0.5 (mins) b) Sample size n= 225 ( round UP to nearest whole numbers) c) So we need more 58 costumers

          Airline Reservations Waiting Time: When customers phone an airline to make reservations, they usually find it irritating if they are kept on hold for a long time. In an effort to determine how long phone customers are kept on hold, one airline took a preliminary random sample of 167 phone calls and determined the average length of time (in minutes each caller was kept on hold). The sample standard deviation was 3.8 minutes. To estimate the true population mean hold times, the researcher wants to use a 95% confidence level.
1) What is the critical value for the 95% confidence level?
Critical value z_c= 1.96 (round answer to 2 decimal places)
2) Please answer three parts a,b,c below to figure out: How many more customers should be included in the sample in order to be 95% sure that the sample mean of holding times is within one-half of a minute of the population mean hold times?
a) The margin of Error E= 0.5 (mins)
b) Sample size n= 225 ( round UP to nearest whole numbers)
c) So we need more 58 costumers

Airline Reservations Waiting Time: When customers phone an airline to make reservations, they usually find it irritating if they are kept on hold for a long time. In an effort to determine how long phone customers are kept on hold, one airline took a preliminary random sample of 167 phone calls and determined the average length of time (in minutes each caller was kept on hold). The sample standard deviation was 3.8 minutes. To estimate the true population mean hold times, the researcher wants to use a 95% confidence level.
1) What is the critical value for the 95% confidence level?
Critical value zc= 1.96 (round answer to 2 decimal places)
2) Please answer three parts a,b,c below to figure out: How many more customers should be included in the sample in order to be 95% sure that the sample mean of holding times is within one-half of a minute of the population mean hold times?
a) The margin of Error E= 0.5 (mins)
b) Sample size n= 225 ( round UP to nearest whole numbers)
c) So we need more 58 costumers

Added by Pedro R.

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