Question

1a. One sample of n1 = 14 individuals (group 1) receive a drug therapy intervention for anxiety. The sum of the squared deviations for the anxiety scores of group 1 was SS1 = 180. Another group (group 2) of n2 = 11 individuals received a pet therapy treatment for anxiety and the sum of the squared deviations for their group SS2 = 120.

a. What is the pooled variance (S2 pooled ) of these two samples? and What is the standard error of the difference between these two samples (Sxଵ̅− xଶ̅)

Answer 1

Answer)

N1 = 14, SS1 = 180

N2 = 11, SS2 = 120

Standard deviation is given by √{ss/(n-1)}

So, s1 = √{180/13} = 3.72

S2 = √{120/10} = 3.46

When the population variances are equal

Standard error = sp√{(1/n1)+(1/n2)}

Sp = √{(n1-1)*s1^2 + (n2-1)*s2^2 }/√{n1+n2-2}

After substitution

Pooled variance sp = 13.027

Standard error = 1.45422581715