satstics

1. Stat lo.6

2. Types of Data
There are two main types of data used in statistical research:
qualitative data and quantitative data.
Qualitative data are measurements that cannot be measured on a
natural numerical scale. For instance, individual’s gender. They
are either male or female and there is no ordering or measuring
on a numerical scale.
Quantitative data are measurements that can be recorded on a
naturally occurring scale. Thus, things like the time it takes to run
a mile or the amount in dollars that a salesman has earned this
year are both examples of quantitative variables.

3. Collecting Data
Common methods of collecting data include the following:
1. Censuses: every ten years. the government conducts a census to
determine the U.S. population.
2. Surveys: Written questionnaires, personal interviews, or telephone
requests for information can be used when experience. preference. or
opinions are sought.
3. Controlled experiments: a structured study that usually consists of two
groups: one that makes use of the subject of the study (for example. a new
medicine) and a control group that does not. Comparison of results for the
two groups is used to indicate effectiveness.
4. Observational study (lies: similar to controlled experiments except that
the researcher does not apply the treatment to the subjects. For example.
To determine if a new drug causes cancer, it would be unethical to give
the drug to patients. A researcher observes (he occurrence of cancer
among groups of people who previous/v took the drug.

4. Organizing Data
1. stem-and-leaf-diagram
2. Frequency distribution table
Height Frequency
40 – 50 1
50 -60 4
60 – 70 10
70 - 80 5

5. Graphing Data
Once the data have been organized. a graph can he used to
visualize their intervals and their frequencies
1. Histogram
Height Frequency
40 – 50 1
50 -60 4
60 – 70 10
70 - 80 5
0
2
4
6
8
10
12
40-50 50-60 60-70 70-80
Height

6. 2. Dot Plot
Height Frequency
40 – 50 1
50 -60 4
60 – 70 10
70 - 80 5
3. Stem Plot
Construct a stem-and-leaf plot for the
following data

7. 4. Box Plot
Construct a Boxplot for the following data
2 51 54 53 43
51 62 49 50 63 60
2 43 49 50 51 51 53 54 60 62 63
Solution
Smallest = 2 Median (Q2) = 51 Largest =63
Lower quartile (Q1) = 49 Upper quartile (Q3) = 60
Inner quartile range (IQR) = 60 – 49 = 11
1.5(IQR) = 1.5(11) = 16.5
Q1 - 1.5(IQR) = 49 – 16.5 = 32.5
Q3 +1.5(IQR) = 60 + 16.5 = 76.5
Smallest outlier = 43
0 10 20 30 40 50 60 70

8. Outlier
It falls more than 1.5 inner quartile range below lower quartile
range or 1.5 inner quartile range over upper quartile range
Center
Median, Mean, and Mode
Spread
Range = Max value – Min value
IQR = Q3 – Q1
Shape
Symmetric, Left or Right Skewed

9. Symmetric Shape
0
2
4
6
8
10
12
40-50 50-60 60-70 70-80 80-90
Height

10. Left Skewed Shape
0
2
4
6
8
10
12
40-50 50-60 60-70 70-80 80-90
Height

11. Right Skewed Shape
0
2
4
6
8
10
12
14
40-50 50-60 60-70 70-80 80-90
Height