All of the dataset sizes are listed in the papers themselves. So these are not really questions. They are attempts to undermine the significance of the work. The simple fact is that tests for statistical significance fully take account of the sample size. If a smaller sample size is used, then a stronger periodicity must be present to get the same level of significance. So that simply proves how strong these periodicities are that they can be consistently detected in small samples.

Although it is relevant to the results what type of galaxies are in the sample, it is not important. I will explain that.

When larger galaxy types only are included then larger quanta are found such as the 72 km/s one. When smaller galaxies are included then the smaller quanta are found as well as the larger. This is made clear by Tifft in his papers and also is consistent with the expectations of Harmonics theory. So whatever types are included one or more periodicities will be found. It is still advisable in future research to examine the periodicities by galaxy type so that thee details of these matters are better understood.
I am fully aware of the use of H I radio observations to measure redshifts. Tifft used these measures to get accurate redshifts in the 1970s.

Your little game with asking silly irrelevant questions to try and find things that I do not know so that you can criticize them is quite irrelevant. There is no need for me to be able to carry out a redshift measurement. All the redshift measurements used in the surveys were taken by astronomers. I am not and astronomer. Your logic on this is inexcusably poor. It would seem that it is a desperate attempt to evade the true conclusions of this research.
Your referring to me with words "she" and "her" when my photo is on hundreds of posts that you have looked at is another example of your attempt to take the conversation into the gutter rather than address the real issues.
Edward R Dewey describes these methods in "Cycles" magazine, and the relevent material is available in the "Cycles Classic Library Collection" published by the Foundation for the Study of Cycles in 1987.
I have stated that the curve is not relevant, the peaks are there without it. I also posted a further graphic based on first differences which shows the periodicity clearly. First differences is effectively differentiation and enhances higher frequency components in a spectrum. Because any selection effects are lower frequency (they have few inflexion points) this method is effective.
Why don't you list them. Then I will prove that none of them can cause a periodicity.
You have the papers of Tiffts as references because you did not believe my statements and wanted peer reviewed material. Now read it!
You apparently missed the other references to a similar period in the papers. Go back and look for 41.5/h Mpc which was reported. This period is visible in every decent sized sample. You can see it in the Broadhurst data along with other fractions of 12,800 km/s.
The facts remain:

1. Every paper that has been published that has sufficently accurate data (as described by Tifft) and looks for smaller scale redshift periodicity in galaxies has found at least one of the quanta 72, 36, 24, 12 km/s and often more than one. There have been many replications and not a single negative result. This is called the scientific method and criticizing sample sizes is not an adequate response because different samples have been used by different researchers.

2. Papers that use the correlation function in 3D do not show these shorter period variations. That proves that they are not spatial structures and that the interpretation of redshift as totally a velocity measurement is wrong.

3. Most papers that have looked at large scale periodicity have found the 12,800 km/s period (z=.043 or 128/h Mpc) and often fractions of this also (1/2 and 1/3). These periods are found using either redshift periodicity or looking for 3D spacings. There are papers that I referenced showing the clear 3D structure as a type of lattice.

4. A number of studies have been performed in special frames to investigate the whole sky synchronization of smaller scale (~72 km/s) redshift periodicities. All published studies confirm the presence of such frames. New data continues to support that conclusion. This totally undermines the conventional interpretation of redshift. If it were correct then the whole universe would be a huge conspiracy to make the centre of our galaxy a very special place. I don't think that anyone believes that.

5. The inescapable conclusion is that Arp and Narlikar are right and that these 72 km/s and such periodicities are changes by steps in redshift over time, and nothing to do with distance. Because the time taken to travel a distance by light is a linear one, it just looks like a distance relationship. However at the distance scale of galaxies the relationship breaks down because there are traveling wavefronts where the redshift of a galaxy will suddenly change by 72 km/s. So you cannot use that information to calculate distances at that scale.

6. In general galaxies cannot be moving even by 20 km/s. If they were, the whole sky periodicity would be destroyed. And it is there for all to see. In fact, it would be destroyed in even galaxy pairs because of the different orientations that we see them at and the 72 km/s difference between them is prevalent.

7. The virial theorum is not a valid basis for anything because it uses the assumption that redshift measures velocity, and it clearly does not.