In a dental study of a tie between infant occlusion and feeding methods, there w
ID: 3174670 • Letter: I
Question
In a dental study of a tie between infant occlusion and feeding methods, there were 27 breast-fed and 60 bottle-fed infants. It was noted that 7 of the breast-fed babies and 26 of the bottle-fed babies developed a related open-bite gum pad in the first 4 months of life. Would you conclude that the bottle-fed group showed a higher proportion of the open-bite gum pad problem?
Perform a chi-square test for significant difference between the two proportions. Use a significance level of .01.
Which statement (A or B) should be the alternative hypothesis for this test?
(A) There is not a difference in the proportions of breast-fed and bottle-fed infants who developed a related open-bite gum pad in the first 4 months of life.
(B) There is a difference in the proportions of breast-fed and bottle-fed infants who developed a related open-bite gum pad in the first 4 months of life.
Fill in the OBSERVED table.
Bottle-fed
Breast-fed
Total
Developed open-bite gum pad
26
7
33
Did not develop open-bite gum pad
34
20
54
Total
60
27
87
Fill in the EXPECTED table. Round to the nearest ones place.
Bottle-fed
Breast-fed
Total
Developed open-bite gum pad
33
Did not develop open-bite gum pad
54
Total
60
27
87
How many degrees of freedom are there?
What is the critical value? 2 = 6.635, 9.21, 3.841, 5.991
What is the test statistic? 2 = 8.86, 2.06, 3.56, 6.76
Which conclusion is correct: A or B?
Conclusion A: There is a not a difference in the proportions of breast-fed and bottle-fed infants who developed a related open-bite gum pad in the first 4 months of life.
Conclusion B: There is a difference in the proportions of breast-fed and bottle-fed infants who developed a related open-bite gum pad in the first 4 months of life.
Bottle-fed
Breast-fed
Total
Developed open-bite gum pad
26
7
33
Did not develop open-bite gum pad
34
20
54
Total
60
27
87
Explanation / Answer
degree of freedom =(row-1)(clumn-1) =(2-1)(2-1)=1
critical value = 2 = 6.635
test statistic? 2 =2.397
Conclusion A: There is a not a difference in the proportions of breast-fed and bottle-fed infants who developed a related open-bite gum pad in the first 4 months of life.
Observed O bottle fed breast fed Total develop 26 7 33 did not 34 20 54 Total 60 27 87 Expected E=rowtotal*column total/grand total bottle fed breast fed Total develop 22.759 10.241 33 did not 37.241 16.759 54 Total 60 27 87 chi square =(O-E)^2/E bottle fed breast fed Total develop 0.462 1.026 1.488 did not 0.282 0.627 0.909 Total 0.744 1.653 2.397