) ▁packets ▁Im pression ▁fra ud ▁▁ ▁Lim itations ▁related ▁to ▁data ▁analysis ▁and ▁distribution ▁flow ▁with ▁impression ▁method ology ▁overcome : ▁ 2 0 . ▁Ad ▁rotation ▁visibility ▁lot tery . ▁Not ▁knowing ▁which ▁ad s ▁in ▁rotation ▁were ▁in ▁view ▁for ▁each ▁ad ▁selection ▁means ▁certain ▁ad s ▁may ▁never ▁be ▁visible ▁making ▁all ▁the ▁stat istic ▁data ▁meaning less . ▁( e . g . ▁ 3 ▁Ad s ▁are ▁in ▁rotation ). ▁For ▁rotation ▁ 1 ▁the ▁ 1 st ▁is ▁in ▁view , ▁ 2 nd ▁is ▁not , ▁ 3 rd ▁is ▁in ▁view . ▁Rot ation ▁ 2 ; ▁ 1 st ▁in ▁view , ▁ 2 nd ▁not , ▁ 3 rd ▁is ▁not , ▁and ▁in ▁ 3 rd ▁rotation ▁the ▁ 2 nd ▁ad ▁is ▁again ▁not ▁in ▁view . ▁All ▁ad s ▁are ▁reported ▁as ▁impress ions , ▁reach , ▁frequency ▁and ▁all ▁other ▁measurements , ▁but ▁ad ▁ 2 ▁was ▁never ▁visible . ▁ 2 1 . ▁Re ach ▁and ▁Fre quency ▁measured ▁for ▁ad s ▁that ▁are ▁not ▁visible . ▁An ▁ad ▁that ▁is ▁not ▁visible ▁did ▁not ▁reach ▁anyone , ▁making ▁reach ▁and ▁frequency ▁measurements ▁meaning less . ▁ 2 2 . ▁Im press ions ▁that ▁are ▁not ▁visible ▁are ▁included ▁in ▁click ▁through ▁rate , ▁making ▁click ▁rate ▁mis leading . ▁ 2 3 . ▁Display ▁of ▁complete ▁brand ing ▁messages ▁and ▁contact ▁information ▁is ▁prohib itive ; ▁If ▁a ▁click - through ▁is ▁necessary ▁to ▁measure ▁advert