Over 589 people have now taken the TAVIS and these have a mean and standard deviation of 9.84 and 2.63 respectively.
When the sample increased to 604, I decided to rank the items by order of difficulty (hat-tip to Kiwi-Anon who suggested this could be easily done in Excel):
At least 48 TAVIS takers reported taking the Wechsler intelligence scales in the U.S. or Canada within the last 10 years (excluding people who reported scores outside the valid score range). This subgroup had a mean TAVIS score of 10.48 (SD = 2.44) and a mean self-reported Wechsler score of 129.92 (SD = 17.61). When I arranged the 48 TAVIS scores from lowest to highest and placed them beside the 48 Wechsler scores ranked lowest to highest, I got the following equivalencies.
TAVIS 7 = Wechsler IQ 100
TAVIS 8 = Wechsler IQ 105
TAVIS 9 = Wechsler IQ 121
TAVIS 10 = Wechsler IQ 125
TAVIS 11 = Wechsler IQ 141
TAVIS 12 = Wechsler IQ 146
TAVIS 13 = Wechsler IQ 151
TAVIS 14 = Wechsler IQ 154
TAVIS 18 = Wechsler IQ 159
Correlation between TAVIS and self-reported Wechsler IQ: +0.04
The correlation with the Wechsler was disappointingly low, but keep in mind that the Mega Test also had an incredibly low correlation with the self-reported Wechsler so this doesn’t necessarily invalidate the test.