This document contains examples of various statistical analyses exercises involving: 1. Categorizing variables as numerical or categorical. 2. Designing a questionnaire and explaining how to enter data. 3. Different sampling methods like simple random sampling, systematic random sampling, stratified random sampling, and cluster sampling. 4. Presenting data in order arrays, frequency distribution tables, and calculating measures of central tendency and dispersion. 5. Explaining the normal distribution and calculating percentages. 6. Calculating confidence intervals and using the chi-square and t-tests to analyze data.

1. 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.

2. 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

3. 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?

4. 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

5. phototherapy
15 6
18 9
14 14
25 26
17 5
20 6
17 4
16.5 3.5

6. phototherapy
15 6
18 9
14 14
25 26
17 5
20 6
17 4
16.5 3.5