A confidence interval is a specific interval estimate of a parameter determined by using data obtained from a sample. 

Confidence Intervals

Concept #1: The percentage in a confidence interval represents the level of certainty that we have for the mean lying within a given range. 

 

Example #1: Construct a 95% confidence interval for an experiment that found the mean temperature for a given city in July as 103.5 oC with a standard deviation of 1.8 from 10 measurements.  

Example #2: The barium content of a metal ore was analyzed several times by a percent composition process.

0.010             0.011             0.004             0.011

Calculate the mean, median and mode. 

Example #3: From EXAMPLE 1, calculate the standard deviation. 

Practice: From the examples given above, find the 90% confidence interval.