Community Medicine

[SUMAN-SAJAN]

STATISTICS QUESTIONS FOR 3RD YEAR FINAL



Group A

1.Suppose it is known that in a certain population 10 percent of the population is colour blind. If a random sample of 25 people is drawn from this population, find the probability that
a) five or fewer will be colour blind
b) six or more will be colour blind
c) between six and nine will be colour blind
d) two, three or four will be colour blind

2.Suppose that 24 percent of a certain population have blood group A. for a sample of 25 people drawn from this population, find the probability that
a) Exactly three will have group A
b) Three or more will have group A
c) Fewer than three will have group A
d) Exactly five will have group A

3. A hospital administrator, who has been studying daily emergency admissions over a period of several years, has concluded that they are distributed according to the poisson law. Hospital records reveal that emergency admissions have averaged three per day during this period. Find the probability that
a. exactly two emergency admissions will occur on a given day.
b. no emergency admission will occur on a given day.
c. either three or four emergency cases will be admitted on a given day.

4. If the mean number of serious accidents per year in a large factory (where the number of employees remain constant ) is five, find the probability that in the current year there will be
a. exactly seven accidents.
b. ten or more accidents.
c. No accidents.
d. Fewer than five accidents.

5. If the capacities of the cranial cavities of a certain population are approximately normally distributed with a mean of 1400 cc. and a standard deviation of 125. Find the probability that a person randomly picked from this population will have a cranial cavity capacity
a. Greater than 1450 cc.
b. Less than 1350 cc.
c. Between 1300 and 1500 cc.


6. If the total cholesterol value for a certain population is approximately normally distributed with a mean of 200mg/100ml. And a standard deviation of 20mg/100ml. Find the probability that an individual picked at random from this population will have a cholesterol value
a. Between 180 and 200mg/100ml.
b. Greater than 225mg/100ml.
c. Less than 150mg/100ml.
d. Between 190 and 210mg/100ml

7. In one study conducted at one VDC in kathmandu the working hour per day for female respondents was found to be 13.85 hours in an average as compared to men with 6.31 hours per day. From similar studies done previously the s. d. was found to be 3.99 hours for female and 4.63 hours for male. Find 90, 95 and 99% C. I. for men and women separately 95% C. I. for the mean difference in working hour. Let no. of females and males be 32.

8. A researcher was interested to estimate urine levels of a certain chemical in pre-term infants with late metabolic acidosis and pre-term infants without the condition. The mean, s. d. and sample sizes are as follows:


Sample n Mean S
With condition 35 8.5 5.5
Without condition 40 4.8 3.6

Find 90, 95 and 99% C. I. for infants with and without condition separately also find 95% C. I. for the mean difference

Group B

9. Researchers wish to know if the data they have collected provide sufficient evidence to indicate a difference in mean serum uric acid levels between normal individuals and individuals with mongolism at 5% level. The data are as follows:

Sample n Mean
Mongoloids 12 4.5 mg/100ml
Normal individuals 15 3.4 mg/100ml
Let the population s. d. for both is 1.


10. Can we conclude that chronically ill children tend on average, to be less self confident than healthy children? A test designed to measure self confidence was administered to 32 chronically ill and 32 healthy children. The mean scores and s. d. were as follows.

Mean S
Ill group 22.5 4.1
Well group 26.9 3.2

11. A study carried out to test the efficacy of the esmolol and lignocaine xylocard, 32 patients each were administered these drug. The mean pulse rate after intubation was found to be 100.7 with s. d. 13.3 for esmolol group and 114.8 with s. d. 17.5 for lignocaine group. Test if the mean pulse rate significantly differs for these drug groups. Also test if the esmolol group mean is more than 90? Let level of significance be 5%.
12. A research carried out to study the risk factors associated with preterm deliveries found that mean no. of ANC in preterm delivery group was 2.5 with s. d. of 1.8. Similarly it was 3.4 with s. d. of 2.1 in term delivery group. Test if the mean ANC visits differs in two groups. Also test if mean is less than 3 for preterm group. Let the no. of samples is 100 for each group.

13. A group of 350 adults who participated in a health survey were asked whether or not they were on diet. The responses by sex are as follows:
Sex
Male Female Total
On diet 14 25 39
Not on diet 159 152 311
Total 173 177 350

Do these data suggest that being on diet is dependent on sex? Let  =. 05

14. A sample of 500 college students participated in a study designed to evaluate the level of college students’ knowledge of a certain group of common diseases. The following table shows the students classified by major field of study and level of knowledge of group of diseases.

Knowledge of disease

Major field Good Poor Total
Premedical 31 91 122
Other 19 359 378
Total 50 450 500
Let =. 05


15. A study of 190 pregnancies yielded the following results on the relationship between hypertension of mother and a certain complication of pregnancy.
Mother hypertensive
A certain complication of pregnancy Yes No Total
Present 23 55 78
Absent 12 100 112
Total 35 155 190
Do these data suggest that the two conditions are not independent? Let  =. 05
=. 05
16. A sample of 500 school children in a certain school system was cross classified by nutritional status and academic performance. The researcher wished to know if they could conclude that there is a relationship between nutritional status and academic performance. Let  =. 05

Academic performance Nutritional status
Poor Good Total
Poor 105 15 120
Satisfactory 20 300 380
Total 185 315 500


17.Following are the data on a study of incidence of miscarriage among women exposed to agricultural pesticides.

Exposed Not Exposed Total
Miscarriage 30 10 40
No miscarriage 70 90 160
Total 100 100 200
Is there any association between two variables? α = .05


18. A team of cardiologists conducted a study to investigate the association between oral contraceptives use and hypertension. Forty women using oral contraceptives and sixty women using other methods of contraception were identified from the records of participating physicians. The proportion of hypertensive patients in each group was recorded as follows.
Hypertensive Normotensive Total
Oral contraceptives 8 32 40
Other 15 45 60
Total 23 77 100
At α = .05 test whether there is any association between hypertension and method of contraception.

19. Five hundred employees of a firm that manufactures a product suspected of being associated with respiratory disorders were cross classified by exposure to the product and whether or not they exhibited symptoms of respiratory disorders. The results are shown in this table. Test at 5% level that the respiratory disorders and exposure.


Symptoms present Yes No Total
Yes 190 45 235
No 150 115 265
Total 305 106 500

Group C

20. Given the correlation coefficient r = 0.8 between two variables height and weight in the sample, state your hypothesis to test the correlation in the population. Interpret your result if p = .02
Similarly interpret your result if p = .35

21. Given the correlation coefficient r = -0.7 in the sample, state your hypothesis to test the correlation in the population. Interpret your result if p = .04
Similarly interpret your result if p = .07

22. Given the two variables X and Y, the line of regression is Y = 29 + 1.53 X
i) Interpret the regression line.
ii) With these sampled values of b = 1.53 if we have to test whether the result is significant in the population, what will be our null and alternative hypothesis?
iii) With b = 1.53, p = .02, interoret the result.
iv) If p = .25, interpret.
v) If the line is Y = 29 - 1.53 X, interpret the line.

23. N = 100 men aged 30 -50 years.
n = 25
Y = 40 + 1.5 X where Y = diastolic BP and X = age in years.
i) Interpret the line.
ii) What is the predicted DBP of 40 year old man?
iii) To carry the significance test, state the hypothesis.
iv) If p is greater than .05, interpret the result.
v) If p is less than .05, interpret the result.

24.Suppose a researcher wants a representative sample of size 100 from the population of households in the VDC. Inquiring the VDC office she found that the total no. of HHs is 1160. she got the list of the hhs from the office.
Which sampling technique should she follow and how? What do you mean by representative sample?
25. The team of researchers wants to carry out a community based research on reproductive health. They found that the total no. of women in reproductive age group is 2200. based on the previous similar type of survey, the sample size for this study is calculated to be 110. they want a representative sample? they want to use systematic sampling technique.
Define the population used in this study.What are the basis to use this sampling technique? Explain the procedure of sampling.

26. In 1000 students studying in certain university, only 20% of the students are female. We have a complete list of the students. We want to carry out a research on knowledge regarding HIV/AIDS. The sample size to be selected is 100.
a. using the probability sampling technique, explain the procedure of the sampling. What is this method called?
b. Using the non probability technique, how a sample of size 100 can be selected?
c. Which method do you think is appropriate? Why?

27. we want to administer a pre and post questionnaire regarding the knowledge on family planning practices to the women of reproductive age group in particular VDC. Since we have to disseminate the report in three months time, we can not study whole VDC. Now we want to choose one ward of this VDC randomly.
a. which sampling technique is to be used to select a ward?
b. Which sampling technique is to be used to select the final sampling elements i. E. women of reproductive age group?

28.in a health camp conducted in one rural district of Nepal, the researchers carried out a study on peak flow measurement of the patients coming to the camp. Which technique is used to select a sample. Is it representative of the entire population?
29.a team wished to conduct a study on road children’ s health status. We do not have any list of these children.
a. How do we select the sample? What is the technique called?
b. If we carry out same sort of study in the rehabilitation centre for these children, what is our sampling technique?

30. a study is carried out to study the health status of commercial sex workers. The population is hard to reach. With lots of efforts, one such lady is found out. Which sampling technique can be used to get the desired sample size?

31. Average wt of baby at birth is 3.05 kg with the sd of 0.39 kg. if the birth wts follow normal distribution will you take
a. wt of 3.9 kg as abnormal?
b. wt of 2.5 kg as normal?

32. Menstrual cycle in women following normal distribution has mean of 28 days and sd of 2 days. How frequently would you expect a menstrual cycle of
a. more than 30 days?
b. less than 20 days?

33. Serum protein is lower in females than in males. Justify this conclusion.
Gender n Mean serum protein sd
Males 40 7.21 0.26
Females 32 6.90 1.28

34. In a group of 196 adults in the age group 45 to 53 years belonging to social class I, the mean serum cholesterol was 180 mg % with sd of 42 mg %. In a comparable group of 144 adults belonging to social class V, the mean serum cholesterol was 150 mg % with sd of 48 mg %. Does the cholesterol level of two social classes differ significantly?

35. In one epidemiological study, of diabetes in urban and rural area of certain zone of Nepal, the following results were obtained.
Area Diabetic Non diabetic Total
Rural 45 3450 3495
Urban 107 3409 3516
Total 152 6859 7011

Does the result differ significantly in two areas?

36.
Sex No. of carriers No.of non carriers Total
Male 78 412 490
Female 57 553 610
Total 135 965 1100
Test whether the prevalence of carrier of filarial is associated with sex.

37. Determine if there is association between scabies amongst the school children and the socio economic status.
Socio economic status
Scabies status I II III IV V Total
With scabies 23 127 640 806 63 1659
Without scabies 427 1573 7560 7526 541 17627
Total 450 1700 8200 8332 604 19286

38. A health researcher wants to estimate the mean hb level in the community. Preliminary information is that this mean is about 150 mg/l with sd of 32 mg/l. if a difference of up to 5 mg/l in either side in the estimate can be tolerated, how many subjects should be included in the study?