1) The FICO credit rating scores obtained in a simple random sample are listed below. As
writing, the reported mean FICO score was 678. Do these sample FICO scores
appear to be consistent with the reported mean?
714 751 664 789 818 779 698 836 753 834 693 802
2) FICO Scores A simple random sample of FICO credit rating scores is
listed below. As of this writing, the mean FICO score was reported to be 678.
Based on these results, is a FICO score of 500 unusual ? Why or why not?
714 751 664 789 818 779 698 836 753 834 693 802
Solution
(1) Ho:mu= 678
Ha:mu not equal to 678
The test statistic is
t=(xbar-mu)/(s/vn)
=(760.9167-678)/(58.28372/sqrt(12))
= 4.93
Assume a=0.05, the critical values are t(0.025, df=n-1=11) =-2.2 or 2.2
Since t=4.93 is larger than 2.2, we reject Ho.
So we cannot conclude that these sample FICO scores appear to be consistent with the reported
mean
(2) P(X<500) =P((X-mean)/(s/vn) <(500-760.9167)/(58.28372/sqrt(12))
=P(Z<-15.51)=0
Since the probability is close to 0, a FICO score of 500 is unusual.
1) The FICO credit rating scores obtained in a simple random sample .pdf
1. 1) The FICO credit rating scores obtained in a simple random sample are listed below. As
writing, the reported mean FICO score was 678. Do these sample FICO scores
appear to be consistent with the reported mean?
714 751 664 789 818 779 698 836 753 834 693 802
2) FICO Scores A simple random sample of FICO credit rating scores is
listed below. As of this writing, the mean FICO score was reported to be 678.
Based on these results, is a FICO score of 500 unusual ? Why or why not?
714 751 664 789 818 779 698 836 753 834 693 802
Solution
(1) Ho:mu= 678
Ha:mu not equal to 678
The test statistic is
t=(xbar-mu)/(s/vn)
=(760.9167-678)/(58.28372/sqrt(12))
= 4.93
Assume a=0.05, the critical values are t(0.025, df=n-1=11) =-2.2 or 2.2
Since t=4.93 is larger than 2.2, we reject Ho.
So we cannot conclude that these sample FICO scores appear to be consistent with the reported
mean
(2) P(X<500) =P((X-mean)/(s/vn) <(500-760.9167)/(58.28372/sqrt(12))
=P(Z<-15.51)=0
Since the probability is close to 0, a FICO score of 500 is unusual
