Exercise 1: Types of variables

Categorize the following variables into either numerical, or categorical

variables.

Age, sex, race, residency, occupation, years of formal education,

cigarettes smoking. No. of cigarettes smoked per day, weight, height,

hemoglobin, anemia, educational level of mother (whether primary,

secondary, college), coffee drinking, No. of cups of tea drunk/day, blood

sugar, blood group, Rh, blood urea, serum sodium.

Exercise 2: Designing a questionnaire form.

The teacher starts by writing the title of the questionnaire on the

blackboard e.g. “Prevalence of smoking habit among medical students in

Erbil”

Then continue by writing each variable (and give some valuable

comments during writing). E.g.

Rank:

Name (optional):

Age (years):

Gender: 1. Male 2. Female

College: 1. Medical college 2. Dentistry college 3. Pharmacy College

Grade:

Smoking: 1. Yes 2. No

If yes: No. of cigarettes/day:

Type of smoking: 1. Cigarettes 2. Arjeela 3. others (specify)………

After that the teacher ask the students to continue by suggesting more

related variables and ask them about their types. .

Lastly the teacher opens the Exel worksheet and give the students an idea

about how to enter the numerical variables, and giving codes for

categorical variables. He writes the names of variables on first row then

enter the data starting from second row.

Exercise three:

Simple random sampling using random number table.

Requirements: Random digit table.

Question:

- Use the random digit table to select 50 students out of 250

students.

- What do you call this type of sampling.

Exercise 4. Systematic random sampling

Question:

Choose 50 students out of 200 students. Mention all steps in details.

Exercise 5. Stratified sampling

Question

One thousand employees (office and manual workers) of an enterprise

were composed of 600 males and 400 females. Use a stratified random

sampling method to collect a sample of 50 males and 50 females.

Exercise 6. Cluster sampling

Question

Use the cluster sampling method to choose a representative sample of

Iraqi primary school students.

Exercise 7

The following are body weight in Kg for 50 students.

Q) Present the data in an order array.

50 82 99 78 59 77 67 79 72 93

55 68 78 99 78 98 56 72 75 94

88 95 78 66 68 92 95 74 74 95

67 71 56 67 89 78 94 59 73 77

45 70 55 78 56 45 56 78 72 83

Exercise 8: The frequency distribution table

Present the following data (marks of students) in a frequency

distribution table:

50 82 99 78 59 77 67 79 72 93

55 68 78 99 78 98 56 72 75 94

88 95 78 66 68 92 95 74 74 95

67 71 56 67 89 78 94 59 73 77

45 70 55 78 56 45 56 78 72 83

Exercise 9: Measures of central tendency and dispersion

For the following data (Blood urea in mg/dl), calculate measures of

central tendency, and measures of dispersion, then present the data in a

proper way or ways.

42 44 30 78 56 30 60 40

41 67 50 35 65 64 49 73

78 56 56 37 72 66 45 49

Exercise ten: The normal distribution

Question 1

Suppose that the mean (+sd) of the marks of students is 70 + 2 and their

distribution is normal.

1.What is the percentage of students whose marks are more than 70?

2. What is the percentage of students whose marks are less than 70?

3. What is the percentage of students whose marks are between 68 and

72?

4. What is the percentage of students whose marks are between 70 and

72?

5. What is the percentage of students whose marks are more than 72?

6. What is the percentage of students whose marks are less than 72?

7. What is the percentage of students whose marks are more than 74?

8. What is the percentage of students whose marks are less than 66?

9. What is the percentage of students whose marks are more than 76?

10. What is the percentage of students whose marks are less than 64?

Question 2

Calculate the 95% and 99% confidence interval for the population mean.

Use the mean and sd of question 1. The sample size is 100.

Exercise 11. The Chi square test

In a study to determine whether there is an association between type of

therapy and outcome in mental illness, a group of 120 mental patients

were given drug and another group of 120 mental patients were given

drug and psychotherapy. The outcome of all patients was registered as

deteriorated, unchanged, or improved. In the first group, 6 of them were

deteriorated and 49 patients were improved. While in the second group,

31 patients were unchanged and 78 patients were improved. At level of

significance 0.05, do these data provide evidence that psychotherapy is

effective measure in treatment of mentally ill patients?

Exercise 12: The t test

Q1: The following values represent SGOT readings (in IU/Liter) of 20

patients affected with liver disease. If you know that the mean SGOT of

the population from which the sample of patients was drawn is 42

IU/Liter. Is there significant difference from the mean of normal

population?

Let alpha = 0.05

34 35 37 40 42 46 46 47 48 49

50 50 55 56 56 56 62 63 65 70

Q2: The weight in gm of two groups of new-born infants was measured.

Mothers of the first group were regular attendants of antenatal care

clinics, while mothers of the second group had no history of such

attendance.

Group1 (Antenatal care)

3000 3500 4000 3200 3150 2950 4100 3750 3450 3200

Group2 (No Antenatal care)

2700 2450 2500 2000 2200 2100 2300 2450 2600 2250

Do these data provide evidence that antenatal care affect the weight of

new-born infants. Let alpha = 0.01

Q3. Eight jaundiced newborns were subjected to phototherapy. Do these

data provide evidence that phototherapy affect bilirubin level?

Bilirubin mg/dl before Bilirubin mg/dl after phototherapy

phototherapy

15 6

18 9

14 14

25 26

17 5

20 6

17 4

16.5 3.5