Answer:
Pooled Standard Error    =0.7157
Step-by-step explanation:
The missing data is
         Mean      n      Std. Deviation    Std. Error
group1 Â Â Â 6.89 Â Â Â Â Â 9 Â Â Â Â Â Â 1.269 Â Â Â Â Â Â Â Â Â Â Â 0.423
group2 Â Â 5.33 Â Â Â Â Â 9 Â Â Â Â Â Â 1.732 Â Â Â Â Â Â Â Â Â Â Â Â 0.577
Standard Error= Std. Deviation / √n
First we calculate pooled standard deviation from the pooled variance formula
Sp²= (n1 – 1)* (s1)² + (n2 – 1) *(s2)²/(n1 + n2 – 2)
   = 8*(1.269)² + 8 (1.732)²/ ( 9+9-2)
   = 12.882888 + 23.998592/16
   =2.3050925
Sp = √ 2.3050925 =1.51825
Pooled Standard Error = Sp *sqrt(1/n1 + 1/n2)
                    =1.51825 *(0.4714)
                     =0.7157