Question

A human factors psychologist is interested in how alcohol impacts driving performance. A sample of participants was randomly assigned into one of three different conditions of alcohol blood levels (abl). The participants then operate a driving simulator and each participant was measured on how much time (in seconds) they spent on a target when steering. The more time they spend on a target, the better their driving skills. What can the psychologist conclude with α = 0.05?

abl 1	abl 2	abl 3
221 192 171 247 234 281 238 171	180 146 178 134 200 170 208 191	184 132 172 137 154 154 176 178

a) What is the appropriate test statistic?
---Select--- na one-way ANOVA within-subjects ANOVA two-way ANOVA

b) Compute the appropriate test statistic(s) to make a decision about H₀.
critical value =  ; test statistic =
Decision:  ---Select--- Reject H0 Fail to reject H0

c) Compute the corresponding effect size(s) and indicate magnitude(s).
η² =  ;  ---Select--- na trivial effect small effect medium effect large effect

Answer 1

a)

within-subjects ANOVA

b)

Applying one way within-subjects ANOVA

Source of Variation	SS	df	MS	F	P-value	F crit
subjects	6314.2917	7	902.0417	1.1017	0.4135	2.7642
Abl	14772.0000	2	7386.0000	9.0204	0.0030	3.7389
Error	11463.3333	14	818.8095
Total	32549.6250	23

critical value = 3.7389   ; test statistic =9.0204

Reject H0

c)

η² =SS(abl)/SS(total)=14772/32549.6250 =0.4538

large effect since η² >0.25