Really confused on calculating/finding the half-equivalence point in a titration curve. This was a lab experiment done in my chem lab. We added 0.0750 M NaOH to acetic acid (pipet 10.00mL of ~0.1M HCH3CO2 into the beaker and add 40mL of DI water).

From my data, the points that jumped were inbetween 13mL and 13.5 mL.

13 mL pH-6.58

13.5 mL pH-10.28

From this jump I calculated my equivalence point at 13.25.

Now what is the half-equivalence point in mL AND pH ?

Really confused on calculating it. I don't think it's just exactly 1/2 (13.25). Because I've seen another student's work who had the same data as me and they calculated their half quiv point in (mL) to be 7.4 and their ph 4.7