7. The level of dissolved oxygen in a river is an important indicator of the water's ability to support aquatic life. You collect water samples at 15 randomly chosen locations along a stream and measure the dissolved oxygen . Here are your results in milligrams per liter: 4.53 , 5.04 , 3.29 , 5.23 , 4.13 , 5.50 ,4.83 ,4.40 , 5.42 , 6.38 , 4.01 , 4.66 , 2.87 , 5.73 , 5.55 Construct a 95% confidence interval for the mean dissolved oxygen level for this stream . Follow the Inference Toolbox . In a study of the effectiveness of weight -loss programs , 47 subjects who were at least 20% overweight took part in a group support program for 10 weeks . Private weighings determined each subject's weight at the beginning of the program and 6 months after the program's end. The matched pairs ttest was used to assess the significance of the average weight loss . The paper reporting the study said , "The subjects lost a significant amount of weight over time , t(46) = 4.68 , P