Low-back pain (LBP) is a serious health problem in many industrial settings. The article Isodynamic Evaluation of Trunk Muscles and Low-Back Pain Among Workers in a Steel Factory (Ergonomics, 1995: 21072117) reported the accompanying summary data on lateral range of motion (degrees) for a sample of workers without a history of LBP and another sample with a history of this malady. Sample Sample Sample Condition Size Mean SD No LBP 28 91.5 5.5 LBP 31 88.3 7.8 Calculate a 90% confidence interval for the difference between population mean extent of lateral motion for the two conditions. Does the interval suggest that population mean lateral motion differs for the two conditions? Is the message different if a confidence level of 95% is used?

Statistics 130M Notes January 19, 2017 notes= January 26, 2017 class Tuesday January 24, 2017 Sick- Skipped Class. Sorry All Thursday January 26, 2017 Chapter 3 Numerical descriptive techniques - Allows us to be precise - Most mathematical calculations Information - When interrupting a histogram we focus on shape Population - Described by parameters - Parameters are often written using greek letters Summaries for symmetric distribution - Central tendency o Balancing point/ halfway point o ***should be same**** o Average of mean o Center of symmetric distribution Skewed distribution - Extreme values/ outliers effected the average - Curve killer - Don’t use balancing point Arithmetic mean