A random sample of 76 people revealed it took an average (mean) of 60 minutes wi
ID: 3315967 • Letter: A
Question
A random sample of 76 people revealed it took an average (mean) of 60 minutes with a standard deviation of 8 minutes for a person to complete a loan application at the bank. Construct a 90% confidence interval for the true time it takes any person to complete a loan form.
LCL = 59.09044447, UCL = 62.60955553
LCL = 58.49044447, UCL = 61.50955553
LCL = 57.99044447, UCL = 63.00955553
LCL = 58.99044447, UCL = 63.10955553
LCL = 57.89044447, UCL = 60.80955553
LCL = 59.09044447, UCL = 62.60955553
LCL = 58.49044447, UCL = 61.50955553
LCL = 57.99044447, UCL = 63.00955553
LCL = 58.99044447, UCL = 63.10955553
LCL = 57.89044447, UCL = 60.80955553
Explanation / Answer
Mean is 60 and s is 8
for 90% confidence the z value is 1.65
thus the LCL is mean-z*s/sqrt(N)=60-8*1.65/SQRT(76) =58.485
also UCL is mean+z*s/sqrt(N)=60+8*1.65/SQRT(76) =61.5 or option B
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