$8\mathrm{.}12$ VALUATION OF SINGLE$-$TENANT PROPERTIES. Refer to The Appraisal Journal $($Summer $2019)$ study of the valuation of single$-$tenant properties. Recall that the ratio of net operating income to property asset value$$called the capitalization rate$$was determined for a sample of $13$ retail property tenants. Data on S&P credit ratings and $5-$year capitalization rates for the $13$ tenants are reproduced in the table. An appraiser wants to compare the mean $5-$year capitalization rate of all single$-$property retail tenants with low $($BBB$-)$ S&P ratings with the corresponding mean for high $($A$,$ AA$-,$ or AA$)$ S&P ratings.

a$)$ Identify the target parameter for this study.

b$)$ Compute a point estimate of the target parameter.

c$)$ What is the problem with using the normal $($z$)$ statistic to find a confidence interval for the target parameter?

d$)$ Find a $90\%$ confidence interval for the target parameter.

e$)$ Use the interval, part d$,$ to make a statement about the difference in mean $5-$year capitalization rates for single$-$property retail tenants with the two S&P ratings.