2.
Complete the problems below.
a. A sample 81 desktop PCs have a mean lifespan of 7.5 years anda sample standard deviation of 3.2 years. Construct a 99%confidence interval for the mean lifespan of desktop PCs.(ROUND TO3 DECIMAL PLACES)
Confidence Interval ( ___________________Q6 ,___________________Q7)
b. When consumers apply for credit, their credit is rated usingFICO scores. Credit ratings are given below for a sample of carloan applicants. Use the sample data to construct a 99% confidenceinterval for the mean FICO score of all applicants for credit.
(ROUND TO THE NEAREST WHOLE NUMBER) assume requirements arefulfilled.
661 595 548 730 791 678 672 491 492 583 762 624 769 729 734706
Confidence Interval ( ___________________Q8 ,___________________Q9)
c. The IQ scores of the normal adult population has a mean of100 IQ points and the standard deviation is 15 IQ points.
Find the sample size needed to estimate the mean IQ ofprofessors given we want 93% confidence that the sample mean iswithin 4 IQ points of the population
mean.
(USE YOUR ANSWER FROM PROBLEM #1a for critical value).
n=_____________Q10
