2. A researcher is testing if different strains of mice are better learners than
ID: 3363082 • Letter: 2
Question
2. A researcher is testing if different strains of mice are better learners than others. She trains mice from three different strains (Strain 1, Strain 2, and Strain 3) on a maze and records the number of errors (wrong turns) each mouse makes. Here are the data: Strain
1 Strain 2 Strain 3 Mean number of errors 13 8.5 7 n 7 7 7
a. Write the hypotheses for a one-way ANOVA comparing the groups. H0: H1:
Continued b. Complete the ANOVA table below using the information on the previous page. SS df MS F Between 136.5 Within 180 Total Calculate Fcrit for ( = .05). Do we reject H0? Write the results in the proper format for an ANOVA.
c. Compute 2 as a measure of effect size.
d. If the results are significant, do we know which strains are significantly different from eachother? Explain why or why not.
Explanation / Answer
Ans:
a)
H0:Number of errors are same using 3 strains.
Ha:Number of errors are different using 3 strains.(i.e. different strains of mice are better learners than others)
b)N=7*3=21
df(between)=3-1=2
df(within)=21-3=18
MS=SS/df
F=MSbetween/MSwithin=6.825
p-value=(6.825,2,18)=0.006
Fcritical=(0.05,2,18)=3.555
As,p-value=0.006<0.05,we reject H0.
c)Effect size=SS(between)/SS(total)=136.5/316.5=0.431
SS df MS F p-value Fcritical Between 136.5 2 68.25 6.825 0.006 3.555 Within 180 18 10 Total 316.5 20Related Questions
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