A student adds too much HCl during the titration, the calculated ksp be too high.
Reason
Ksp refers to solubility product. It is a measure of solute present in solution. Now, when a sparingly solution base, like calcium hydroxide, is titrated with an acid, like HCl. The reaction results in generation of salt (in present case CaCl2) and water. The solubility of salt is higher as compared to sparingly soluble base. So during the course of reaction, Ca^2+ ions present in system will combine with Cl^- ions to form CaCl2. This will result in decreasing in conc. of Ca^2+ ions in solution. To compensate for this lose, more Ca^2+ ions from Ca(OH)2 will dissolve in solution. Thus, Ksp value will increase.