The researchers observed a random sample of mating pairs. The spiders had all been identified and measured before the mating occurred spontaneously. Is there evidence that male and female orb‑weaver spiders in mating pairs differ significantly in body length? Select the inference procedure you would consider and the corresponding null and alternative hypotheses.

Null hypothesis: male and female spiders organized in mating pairs don't differ significantly in respect to body length

Alternative hypothesis: male and female spiders organized in mating pairs exhibit significant differences in respect to body length

The application of one statistical test in order to obtain one p-value (probability value) may provide useful evidence to support the alternative hypothesis (or reject it).  

The inference procedure uses the information collected from the sample in order to obtain one conclusion.  Frequentism is a type of inference procedure that can be used to test a hypothetical test case, which is here represented by male and female spiders organized in mating pairs.

the tricuspid valve is present between right atrium and right ventricle

answer; both surfaces of the membrane are nonpermeable