Albert Abbasi, VP of Operations at Ingleside International Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff prepared the following distribution of waiting time for walk-in customers.
Waiting Time Number of Customers
(in minutes)
0-under 2 60
2-under 4 30
4-under 6 10
The standard deviation of waiting time for this sample of walk-in customers is ______.
A. 2 minutes
B. 1.35 minutes
C. 1.82 minutes
D. 1.80 minutes
Answers
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Answer:
option B) 1.35 Min
Step-by-step explanation:
Mean ={ (0+2)/2) * 60 + ((2+4)/2 ) * 30 +( (4+6)/2 ) * 10 }/(60 + 30 + 10)
= (60 + 90 + 50)/100
= 200/100
= 2
σ² = {60 * (1-2)² + 30*(3-2)² + 10(5-2)² }/(60 +30 + 10)
=> σ² = ( 60 + 30 + 90)/100
=> σ² = 180/100
=> σ² = 1.8
=> σ = √1.8
=> σ = 1.34 min
close to 1.35 min
option B
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