In a comparison of visual acuity of deaf and hearing children, eye movement rate
ID: 3170937 • Letter: I
Question
In a comparison of visual acuity of deaf and hearing children, eye movement rates are taken on 8 deaf and 8 hearing children. A clinical psychologist believes that deaf children have greater visual acuity than hearing children. Test the psychologist's claim by using the data in the table. (The larger a child's eye movement rate, the more visual acuity the child possesses.) Let alpha = 0.05. Ho: The visual acuity of the two groups is identical. Ha: The visual acuity of the deaf children is greater than the visual acuity of the hearing children. Rank the combined data and calculate the Wilcoxon test statistic T. This is a rank sum test. Specify the critical region. Make a decision about Ho.Explanation / Answer
we shall conduct the analysis using the open source statistical package R , the complete R snippet is as follows
deaf<- c(2.45,3.14,3.23,2.3,2.64,1.95,2.17,2.45)
hearing<- c(1.15,1.65,1.43,1.73,1.75,1.33,2.03,1.64)
wilcox.test(deaf,hearing)
The results of the test are
Wilcoxon rank sum test with continuity correction
data: deaf and hearing
W = 63, p-value = 0.001348
alternative hypothesis: true location shift is not equal to 0
as the p value is less than 0.05 , hence we can safely reject the null hypothesis H0 and conclude that the visual acuity of the deaf children is greater than that of the hearing children
here n = 8-1 = 7
the critical value is 2 using the wilcox table for alpha = 0.05