The following is a random sample taken from the data that represents the time intervals in days between earthquakes that either registered magnitudes greater than 7.5 on the Richter scale or produced more than 1000 fatalities during the time period December 1902 to March 1977.
263 1901 121 832 150 99
(a) Construct a 95% jackknife con?dence interval for the average number of days between earthquakes of this type.
(b) Give an approximate 95% jackknife con?dence interval for the population variance of number of days between earthquakes of this type.