A dentist is interested in obtaining information about
delinquent (past due) accounts. Since the practice opened 12 years
ago, delinquent accounts are normally distributed with an average
of 47 days and a SD of 10 days. The dentist randomly
selected a sample of 29 delinquent accounts with an average of 47
a) The dentist wants to know what average number of days is less than 66% from the past 12 years.
b) Is the average days from the sample of 29 more than the 66% average from the past 12 years?
let X is value of delinquent accounts
so as given that X is normal distribution with
sample size =n=29
let "u" is average value that is less than 66% from the past 12 years so
from Z table
P(Z>-0.412)=0.66 so on comparing
so required value is 46.235
sample avearge ==47
since only 50% of values less than the sample average hence its not more than 66% of averages
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