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  \subsection{The Liu Quasar Pair Catalogue}  The data quasar pair catalogue  sample used in this project is obtained from Lui et al 2011. The purpose of the Lui's selection  criteriaadopted by Lui in selecting data points for the Quasar Pair Catalogue  is to refine compile (from  the AGN sample from the parent sample to SDSS)  a sample Quasar Pair catalogue  of interacting AGN pairs only. AGN (Liu et al 2011)AGN  pairs that make up the parent sample are identified optically from the spectroscopic sample of the SDSS DR7. Lui et all 2011, answers the question: are all the AGN pairs in Further selection criteria is applied to refine  the parent sample to be included in ensure  the study? study of genuinely interacting AGN pairs rather than chance superpositions.  Using line of sight (LOS) velocity differences (or offset) where LOS velocity is the velocity meausured along the line of sight of an observer,  and transverse separation, separation - the projected distance within the LOS direction -  rp ,Lui selects only AGN pairs that are interacting. The choice to use projected separations rp < 100h70-1 kpc to refine the sample space – remove pairs that are closely separated at low separation  but are not interacting. Lui further observes that most pairs with separation greater than 100 kpc are found to be closely separated but not interacting with one another. Selecting those with separation less than 100 kpc helps remove these points that are not a part of our sample space. It is surprising to note that 100 kpc is larger than the thresholds used in other galaxy pair studies namely (Barton et al. 2000; Ellison et al. 2008; Darg et al. 2010), but lui does not explain why 100 kpc is used as the threshold. Lui further Justifies the use a LOS velocity offset (Δv) < 600 km s-1 as a method to further refine the desired sample space. Observing the distribution of (Δv) of AGN pairs (figure (2) provided in Liu) shows us that that most AGN pairs are found within the 300 ≲ (Δv) < 600 km s-1 interval. Even so, Lui et all further states that Δv range within which the pair is still interacting depends on the environment – there could be a chance that some data point were erroneously cut from the sample.  Visual inspection of SDSS images for spectroscopically selected images further removes 34 AGN pairs from the parent sample. Perhaps their spectroscopic profiles do not match those of interacting pairs. What was the criteria for this- is still left unanswered.  Lui also notes possible outliers and common trends in our refined sample space. The surprising, sixteen data points with z> 0.16 ,which seem to be outliers are kept in our sample. They are said to reduce uncertainties at higher red-shifts.