Suppose a researcher wishes to construct a 99%-

t-confidence interval for the difference of two independent means with unknown population standard deviations. His sample sizes are

1

=7

n1=7and

2

=10,

n2=10,and his calculated Satterthwaite approximate degrees of freedom are 12.513.

What is the positive

tcritical value for this confidence interval, rounded to 3 decimal places?