## 1.2 Collection, Presentation, and Organization of Data

• Qualitative
• Quantitative

### 1.2.2 Sources of Data

• Primary: Obtained directly (not collected from someone else)

• Secondary: Using pre-collected data from someone else/some organization

Example (Guess Types)

• A researcher buys data from BMD to build a model of rainfall behavior
• A researcher runs an experiment to measure speed of light using a novel technique.
• A researcher makes use of the data generated by the one in example 2

### 1.2.3 Method of Data Collection

• Direct personal Inquiry

• Indirect oral inquiry

• Mail

• Telephone etc.

### 1.2.4 Sources of Secondary Data

• Published: Scientific Journals, Newspapers etc.
• Unpublished: BBS, WHO, IMF, FAO, ICDDR,B

### 1.2.5 Disadvantages of Secondary Data

• Purpose might be different
• Suitability
• Reliability
• Unit

### 1.2.7 Data Classification

• Geographical
• Chronological
• Quantitative
• Qualitative

### 1.2.8 Example

Geographical
GDP(m) 120 500
Chronological (Time series data)
Year 2015 2016
GDP(m) 120 500
Quantitative Classification
Income level 40,000-50,000 50,000-1,00,000
Frequency 120 34

### 1.2.9 Histogram

• Inclusive vs exclusive

What does it tell us

### 1.2.10 Histogram Intervals

Can these intervals be readily used?

(5-10); (10-15); (15-20)

(5-9); (10-14); (15-20)

If not, what should we do?

### 1.2.11 Stem and Leaf

• key in stem and leaf plot
• How to interpret stem and leaf plot
data <- c(16, 26, 12, 10, 27, 30, 14,  1, 25, 20)
stem(data)
##
##   The decimal point is 1 digit(s) to the right of the |
##
##   0 | 1
##   1 | 0246
##   2 | 0567
##   3 | 0

### 1.2.12 How to interpret cf and rf

Class Frequency Cumulative

Frequency (cf)
Relative

Frequency (rf)
Cumulative

Relative

Frequency (crf)
30-35 4 4 0.09 0.09
35-40 10 14 0.23 0.32
40-45 20 34 0.45 0.77
45-50 8 42 0.18 0.95
50-55 2 44 0.04 1
n=44 n=44

### 1.2.14 Bar vs Pie

• When to use which?
• How to calculate angles?
• Can we draw on 180 degrees?

### 1.2.15 Choose Diagram

year Sales (\$)
1996 76
1997 58
1998 95
1999 85

Category Cost(Tk.)
House rent 10,000
Utility Bill 3,000
Telecom 2000