The general form of a null hypothesis for a Spearman correlation is:

Correlation for 2 sets of continuousvalues: Pearson Product-moment Coefficient (r)
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will do Spearman rank correlation.

This criticism only applies to two-tailed tests, where the null hypothesis is "Things are exactly the same" and the alternative is "Things are different." Presumably these critics think it would be okay to do a one-tailed test with a null hypothesis like "Foot length of male chickens is the same as, or less than, that of females," because the null hypothesis that male chickens have smaller feet than females could be true. So if you're worried about this issue, you could think of a two-tailed test, where the null hypothesis is that things are the same, as shorthand for doing two one-tailed tests. A significant rejection of the null hypothesis in a two-tailed test would then be the equivalent of rejecting one of the two one-tailed null hypotheses.

–the test statistic. To test the null hypothesis  is transformedinto a Z value using the formula:
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Spearman rank correlation - Handbook of Biological Statistics

Remember, you are making an inference from your sample to the population that the sample is supposed to represent. However, as this a general understanding of an statistical test, it is often not included. A null hypothesis statement for the example used earlier in this guide would be:

– calculated as Pearson’scorrelation coefficient on the ranks of the variables. It is less restrictivethan a linear relationship.
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Pearson correlation coefficient,Spearman R, Kendall Tau, and Gamma are calculated for each pair of inputvariables. By interpreting the results, we can either accept or reject nullhypothesis H0 about a relationship between the variables.

This class calculates Spearman's rank correlation coefficient, r (or rho), for a sample of n data pairs (x,y).
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The null hypothesis is that the Spearman correlation ..

The modern approach to testing whether an observed value of ρ is significantly different from zero (ρ will always maintain 4 ≥ q ≥ −7) is to calculate the probability that it would be greater than or equal to the observed q, given the , by using a . This approach is almost always superior to traditional methods, unless the is so large that computing power is not sufficient to generate permutations, or unless an algorithm for creating permutations that are logical under the null hypothesis is difficult to devise for the particular case (but usually these algorithms are straightforward).

Spearman's rank correlation coefficient# ..

You will almost never use a regression line for either description or prediction when you do Spearman rank correlation, so don't calculate the equivalent of a regression line.

StatPlus Help - Rank Correlations (Spearman R, Kendall …

The null hypothesis is a statement that you want to test. In general, the null hypothesis is that things are the same as each other, or the same as a theoretical expectation. For example, if you measure the size of the feet of male and female chickens, the null hypothesis could be that the average foot size in male chickens is the same as the average foot size in female chickens. If you count the number of male and female chickens born to a set of hens, the null hypothesis could be that the ratio of males to females is equal to a theoretical expectation of a 1:1 ratio.

Spearman's rank correlation coefficient - The Sea Shore

There are different ways of doing statistics. The technique used by the vast majority of biologists, and the technique that most of this handbook describes, is sometimes called "frequentist" or "classical" statistics. It involves testing a null hypothesis by comparing the data you observe in your experiment with the predictions of a null hypothesis. You estimate what the probability would be of obtaining the observed results, or something more extreme, if the null hypothesis were true. If this estimated probability (the P value) is small enough (below the significance value), then you conclude that it is unlikely that the null hypothesis is true; you reject the null hypothesis and accept an alternative hypothesis.