for the results of an experiment to be truly reliable, . the data must be exactly what the hypothesis predicted data should only be collected on only the factors that have shown a reaction the sample groups must be different enough to account for errors in the data the experiment must be repeated several times with similar results

Answer is: the equilibrium  shifts toward the reactants, to the left side of chemical reaction.it is because lead(ii) nitrate dissociates in water: pb(no₃)₂ → pb²⁺(aq) + 2no₃⁻(aq).according to lechatelier's principle, the position of equilibrium moves to counteract thechange (more lead cations, common ion), the position of equilibrium will move so that the concentration ofproducts decrease and concentration of reactants of chemical reaction increase.read more on -