At a ski resort, water at 40 F is pumped through a 3-in.-diameter, 2000-ft-long steel pipe from a pond at an elevation of4286 ft to a snow-making machine at an elevation of 4623 ft at arate of 0.26 ft3/s. If it is necessary to maintain a pressure of 180 psiat the snow-making machine, determine the horsepower added tothe water by the pump. Neglect minor losses.
Chapter 4: What is the difference between a test group and a control group A test group is composed of subjects who receive a treatment that the researcher believes is causally linked to the dependent variable. A control group is composed of subjects that don’t receive the treatment. What is meant by a rival explanation A rival explanation is an alternative cause for a change or not in a dependent variable. What is selection bias and how does it relate to random selection Selection bias occurs when nonrandom processes determine the composition of the test and control groups. Random selection is the opposite of selection bias, where the control and test groups are picked randomly. What is meant by internal and external validity Which one does a true experiment promote Internal validity means that, within the conditions created artificially by the researcher, the effect of the independent variable on the dependent variable is isolated from other plausible explanations External validity means that the results of a study can be generalized and applied to situations in the natural, uncontrolled world A true experiment promotes internal validity because the environment is controlled and only one variable is manipulated. What is meant by a spurious relationship In a spurious relationship, the control variable defines a large compositional difference across values of the independent variable. It means that the control variable is interacting with experi