What is the main purpose of hypothesis testing in statistics?

Which of the following is always true about the null and alternative hypotheses?

A multinomial-logit mode choice model has been estimated to determine the split in person-trips among three modes: drive-alone (DA), shared-ride (SR), and transit (TR). The following are the utility expressions: The probability of choosing the transit mode is: Pr(TR) =   1. The total demand for travel from a residential zone to the CBD = 1000 person trips. Assume the following “base-level” transportation system characteristics and calculate the transit ridership and revenue under this base case scenario.    2. To alleviate congestion and improve air-quality, two options are proposed: (a) “Free Transit” – there is no charge to ride the transit (cost = 0 and IVTT and OVTT for transit remains at the base level). (b) “Frequent Transit” – increase the frequency of the buses so that the travelers’ OVTT for transit is reduced to 12 minutes (IVTT and Cost for transit remains at the base level). The service characteristics of the other two modes (DA and SR) remain at base level under all scenarios. Considering transit ridership and revenue under the base case and the two scenarios, which one would you recommend? Show relevant calculations.    

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The figure below represents a simple network with one origin (O), one destination (D), two internal nodes (1 and 2), and five network links. In this case, the link travel times vary linearly as a function of the flow on the links as shown in the figure.  The demand for travel between the origin and destination is 100 trips. Consider a situation in which 65 vehicles choose route O-1-D (i.e. q1 = q4 = 65) and the rest (i.e., 35 vehicles) choose route O-2-D.  No one chooses O-2-1-D. Show using appropriate calculations that this situation does NOT represent user equilibrium. At equilibrium, will the flow on O-1-D be greater than 65 or lesser than 65? Note that you do not have to solve the equilibrium flows.    

The figure below represents a simple network with one origin (O), one destination (D), two internal nodes (1 and 2), and five network links. The link travel times are also indicated on the figure.  In this case, the link travel times are a constant (i.e., do not vary as a function of link flows). The demand for travel between the origin and destination is 100 trips. Based on an “all-or-nothing” assignment scheme, determine the flows on each link of the network. What would be the link flows at user-equilibrium? Present your answer in the form of a table as shown below (you can insert a table in your answer space) Link All-or-nothing flow User equilibrium flow O-1     O-2     2-1     2-D     1-D        

Inhibition of glucose-6-phosphate dehydrogenase (G6PD) would most directly impair which of the following cellular processes?  

Which of the following best explains why substrate-level phosphorylation during glycolysis can still proceed efficiently even when intracellular ATP concentrations are elevated?  

During vigorous muscle contraction, which of the following allosteric signals would most directly enhance ATP production by activating multiple enzymes in the TCA cycle and glycolysis?

A toxin specifically inhibits electron transfer from NADH to FMN at Complex I of the mitochondrial electron transport chain. Which of the following is the most immediate metabolic consequence of this inhibition?