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Factors affecting jet deflection
Clearly the dipole moment of the molecules involved will have a major effect on the deflection of the jet, but a number of other important factors need to be considered.
The distance between the charged rod and the jet is probably the most significant. You will see a range of deflections during the video clip in the experiment as the charged rod is held against the jet. A set up to keep a fixed distance, and not to rely on a steady hand (or otherwise!), would have eliminated this error.
The degree of charging of the rod is difficult to keep constant. Charge is lost from the rod so it needs to be freshly charged by rubbing before each experiment. A higher charge on the rod will mean a greater degree of deflection.
The velocity of the liquid will affect the deflection. If it is moving more quickly it will spend less time as it passes the rod and so be deflected less. The velocity of the jet will depend on the height of liquid in the burette.
The density of the liquid is another factor. Less dense liquids will be easier to deflect than more dense ones.