How many references should I include in a PhD thesis?

Before I wrote my PhD thesis, I went to Warwick Library and picked up one thesis of my senior. I calculated the number of references she included in her thesis, and I found the following figures:

443 references

34 tables

16 figures

7 chapters (excluding introduction)

2 appendices (Questionnaire used)

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After I wrote my PhD thesis, I calculated mine. Herewith my figures for my postgraduate students to refer:

266 references (including 32 references to dictionary or encyclopedia)

(top-down; synthesis; reflexion; perception; pedagogy; pattern matching; pattern; new media; narrative; meta; medium; map; issue; industry; game theory (2); game (3); evolution; engage; electronic game; edutainment; education; creative industries; concept (4); bottom-up; attitude; analysis) 

67 tables

35 figures

9 chapters

16 appendices