Question

A researcher conducts an independent samples study examining the effect of distractions on memory performance. He randomly selected two groups of participants. The experimental group was given a memory test when there were distractions in the lab and the control group completed the same memory test without any distractions. The collected data are as follows:

Experimental Group (Distractions):      Control Group (No Distractions):

n = 21                                                     n = 21

M = 64                 M = 67

SS = 260                SS = 220

Based on the collected data, is there a significant effect of distractions on memory performance?  Use p < .05, 2-tails test to answer this research question.

Answer 1

Null hypothesis, ho: there no significant effect of distractions on memory performance. u1=u2
Alternative hypothesis, h1: there a significant effect of distractions on memory performance. u1 =/= u2

	sample 1	sample 2
n=	21.000	21.000
mean=	64.0000000	67.0000000
s=	SQRT(260/20) = 3.6055513	sqrt(220/20) = 3.3166248
s^2/n	0.6190	0.5238

Sp^2
{(n1-1)*s1^2 + (n2-1)*s2^2} / {n1+n2-2}
=((21-1)*3.60555127546399^2+(21-1)*3.3166247903554^2)/(21+21-2)
12.0000

Test statistic, t = (Xbar1 - Xbar2)/sqrt(Sp^2*(1/n1+1/n2))
t = (64-67)/SQRT(12*(1/21+1/21))
t = -2.8062

df= n1+n2-2
21+21-2
40

p-value
2*(1-P(T<|t|)
2*(1-P(T<abs(-2.8062))
T.DIST.2T(abs(-2.8062),40)
0.0077

With t=-2.8, p<5%, i reject Ho and conclude that there no significant effect of distractions on memory performance. u1=u2