I am having trouble
I am working on a problem here. It is a sample of 9 bonds taken from a normally distributed population. The population has a mean of 16% and a variance of 144. If a bond is selected at random, a 90% confidence interval for its return is:
My thought here was that i’d use the t-table (also tried Z to be clear) using the df to get the t-stat(or z) and multiply by the standard error i calculated as the Std Dev of 12/ sqrt9 and then +/- this value from the mean to get a range for the confidence interval. But doing this seems to not get me anywhere.
I’m worried I am simply doing this all wrong and im not catching on. Any guidance is appreciated.
(the correct answer on this according to my book is -3.74% to 35.74%)