Answer:
Option a
Step-by-step explanation:
Given two normal distribution samples
I group has 106 as mean and 8.5 as std deviation with sample size = 60
II group has 121 as mean and 6.3 as std deviation with sample size =38
We find mean difference =-15
For margin of error finding, we have to find the combined std error for the difference
Variance of difference = Sum of variances
STd error for difference = 1.50
Hence for 99% margin of error =2.58(1.50)
= 3.87
