null hypothesis

hypothesis /hy·poth·e·sis/ (hi-poth´ĕ-sis) a supposition that appears to explain a group of phenomena and is advanced as a basis for further investigation.

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alternative hypothesis  one that is compared with the null hypothesis in a statistical test.

biogenic amine hypothesis  the hypothesis that depression is associated with deficiency of biogenic amines, especially norepinephrine, at functionally important receptor sites in the brain and that elation is associated with excess of such amines.

jelly roll hypothesis  a theory explaining the formation of nerve myelin, which states that it consists of several layers of the plasma membrane of a Schwann cell wrapped spirally around the axon in a jelly roll fashion.

lattice hypothesis  a theory of the nature of the antigen-antibody reaction which postulates reaction between multivalent antigen and divalent antibody to give an antigen-antibody complex of a lattice-like structure.

Lyon hypothesis  the random and fixed inactivation (in the form of sex chromatin) of one X chromosome in mammalian cells at an early stage of embryogenesis, leading to mosaicism of paternal and maternal X chromosomes in the female.

null hypothesis  the particular one under investigation, which frequently asserts a lack of effect or of difference.

one gene–one polypeptide chain hypothesis  a gene is the DNA sequence that codes for the production of one polypeptide chain. Antibodies are an exception; separate genes for variable and constant regions are rearranged to code for a single polypeptide.

response-to-injury hypothesis  one explaining atherogenesis as initiating with some injury to the endothelial cells lining the artery walls, which causes endothelial dysfunction and leads to abnormal cellular interactions and initiation and progression of atherogenesis.

sliding filament hypothesis  the stretching of individual muscle fibers raises the number of tension-developing bridges between the sliding contractile protein elements (actin and myosin) and thus augments the force of the next muscle contraction.

Starling's hypothesis  the direction and rate of fluid transfer between blood plasma in the capillary and fluid in the tissue spaces depend on the hydrostatic pressure on each side of the capillary wall, on the osmotic pressure of protein in plasma and in tissue fluid, and on the properties of the capillary walls as a filtering membrane.

wobble hypothesis  one describing how a specific transfer RNA (tRNA) molecule can translate different codons in a messenger RNA (mRNA) template. It states that the third base of the tRNA anticodon does not have to pair with a complementary codon (as do the first two) but can form base pairs with any of several related codons.

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null hypothesis (H₀),

(in research) a hypothesis that predicts that an observed difference is due to chance alone and not a systematic cause.

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null hypothesis,

n theoretical assumption that a given therapy will have results not statistically different from another treatment.

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null hypothesis,

n a statistical hypothesis that predicts that no difference or relationship exists among the variables studied that could not have occurred by chance alone.

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null

an absence of information, as contrasted with zero or blank or nil, about a value.

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null cell

called also null lymphocyte; see null cell.

null hypothesis

a statistical hypothesis which states that one variable has no association with another variable, or set of variables. That is, the observed results can be explained by chance alone.

null lymphocyte

see null cell.

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null hypothesis

Statistics A hypothesis that assumes that if there are no differences between 2 populations–or sets of data being compared, a statement of probabilities–P value can be made; the proposition, to be tested statistically, that the experimental intervention has "no effect," meaning that the treatment and control groups will not differ as a result of the intervention. The NH is a statistical assumption based on data which demonstrates an association of 2 events or factors in > 95% of cases. See Hypothesis testing. Cf Alternative hypothesis.