HESC 500 Chi Square Test
1) In a study on the effects of dental hygiene instruction on dental caries in children, 100 children were randomly selected; 50 received instruction and 50 did not. At the end of a 6-month period, the number of new cavities for each child was recorded. The data is given below.
Number of New Cavities
0-1 2-3 4-5 Total
Instruction 30 15 5 50
No instruction 20 15 15 50
100
Using the 5 percent level of significantly, can it be said that there is an association between instruction in dental hygiene and number of new Cavities at the end of the 6-month period?2) Fort females using oral contraceptives and 60 females using other contraceptive devices were randomly selected, and the number of hypertensive for both groups were recorded as follows:
Total No. Hypertensives
Oral contraceptives 40 8
Other 60 15
Test the hypothesis that the proportion of patients with hypertension is the same for the two groups. (Use 0.01.) Construct a 99 percent confidence interval on the true difference in proportion hypertensive for the two groups.
3) In order to examine the effects of tranquilizers and stimulants on driving skills, 150 people selected at random were given either a stimulant, a tranquilizer, or an identically appearing placebo. After receiving the medication, the participants were given a battery of coordination and reaction time tests and the number of mistakes for each was recorded. The following table gives total number of mistakes for the entire battery of tests for the three groups:
Total Number of Mistakes
0-5 6-10 11-15 Total
Stimulant 10 20 20 50
Depressant 5 15 30 50
Placebo 25 15 10 50
150
4) Freshman medical students were asked to rate a particular core course according to level of difficulty of the material presented in lectures. The following table shows this response cross-tabulated with grade relieved in the course:
Perceived Difficulty of Course
Class Rank (Final grade) Not Difficult Intermediately Difficult Very Difficult Total
Upper 1/3 10 40 17 67
Middle 1/3 20 35 12 67
Lower 1/3 21 15 30 66
200
Is there an association between Perceived difficulty of the course and class rank? (Use 0.05)
