Suppose an unknown radioactive substance produces 12800 counts per minute on a geiger counter at a certain time, and only 800 counts per minute 10 days later. assuming that the amount of radioactive substance is proportional to the number of counts per minute, determine the half-life of the radioactive substance.

Use the given degree of confidence and sample data to construct a confidence interval for the population mean mu . assume that the population has a normal distribution. a laboratory tested twelve chicken eggs and found that the mean amount of cholesterol was 185 milligrams with sequals 17.6 milligrams. a confidence interval of 173.8 mgless than muless than 196.2 mg is constructed for the true mean cholesterol content of all such eggs. it was assumed that the population has a normal distribution. what confidence level does this interval represent?