When we use past simple and present perfect?

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?

Perform the indicated operation and write the answer in the form a + bi. (-5 + 2) + (3 - 6i)

Ahyperbola centered at the origin has a vertex at (-6,0) and a focus at (10,0). what are the directrices?