The following observations are lifetimes (days) subsequent to diagnosis for individuals suffering from blood cancer. 115 181 255 418 441 461 516 739 743 789 807 865 924 983 1025 1062 1063 1165 1191 1222 1222 1251 1277 1290 1357 1369 1408 1455 1478 1519 1578 1578 1599 1603 1605 1696 1735 1799 1815 1852 1899 1925 1965 a. What do we mean by condence interval? Explain. b. Calculate and interpret a confidence interval with a 99% confidence level for true average lifetime