• Question: An individual’s critical flicker frequency (cff) is the highest
frequency, in cycles per second (cps), at which the flicker in a flickering
light source can be detected. At frequencies above the cff, the light
source appears to be continuous even though it is actually fllickering. A
study was carried out to see if the mean cff depends on iris color.
• Data Collection: Individuals with blue, brown and green eyes were
chosen at random to participate in the study.
• Data: Critical flicker frequency in cycles per second.
Eye Color
Blue Brown Green
25.6 23.9
24.5
27.0 24.5
25.4
27.8 24.8
25.8
28.0 25.0
26.4
28.3 25.7
26.7
28.5 26.5
26.9
29.4 27.0
28.0
30.2 28.2
29.1
Y i. 28.1
s2i 1.98
• Formulas:
SSM odel =
25.7
2.08
k
26.6
2.12
ni (Y i. − Y .. )2
i=1
SSError =
i
2
(Yij − Y i. ) =
(ni − 1)s2i
i=1
j
SST otal =
k
i
j
(Yij − Y .. )2