Question

Forty-five participants (15 per group) were randomly assigned to do a series of math tasks while listening to Soft-Gentle music (M = 37), Loud-Intense music (M = 33) and in Silence (M = 41). The researcher found a significant difference across the groups and predicted that the difference lies between soft-gentle music and silence. With MS_within given as 25, conduct a planned contrast between these two groups (using significance level of .05).

To receive full marks ensure that you include the numerator and denominator for your F ratio.

Answer 1

NULL HYPOTHESIS H0:

ALTERNATIVE HYPOTHESIS HA: AT LEAST TWO MEANS ARE DIFFERENT

LEVEL OF SIGNIFICANCE =0.05

K=3

n1=n2=n3= 15

SOURCE	S.S	D.F	M.S	F	PVALUE
BETWEEN GROUPS	480	2	240	9.6025	0.0004
WITHIN GROUPS	1049.7228	42	24.9934
TOTAL	1529.7228	44

F CAL= 240/24.9934= 9.6025

F CRIT WITH DF1=2 AND DF2= 42 AT 0.05 IS 3.22

CONCLUSION: SINCE F CAL IS GREATER THAN F CRITICAL, WE REJECT NULL HYPOTHESIS AT 0.05 LEVEL OF SIGNIFICANCE. YES, THERE IS A DIFFERENCE IN PERFORMANCE ON THIS KIND OF MATH TASK UNDER THESE THREE CONDITIONS.

EFFECT SIZE = SS BETWEEN/ S.S TOTAL= 480/1529.7228= 0.3137 IS MEDIUM

RIGHT TAIL F DISTRIBUTION

LEFT TAIL DISTRIBUTION