統計學 Fall 2003. 授課教師：統計系余清祥 日期：2003年9月16日 第一週：什麼是統計？. 什麼是統計?. 統計學是研究定義問題、運用資料蒐集、整理、陳示、分析與推論等科學方法, 在不確定( Uncertainty) 情況下, 做出合理決策的科學。. Chapter 1 Data and Statistics. Applications in Business and Economics Data Data Sources Descriptive Statistics
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統計學 Fall 2003
授課教師：統計系余清祥
日期：2003年9月16日
第一週：什麼是統計？
什麼是統計?
Public accounting firms use statistical sampling procedures when conducting audits for their clients.
Financial advisors use a variety of statistical information, including price-earnings ratios and dividend yields, to guide their investment recommendations.
Electronic point-of-sale scanners at retail checkout counters are being used to collect data for a variety of marketing research applications.
A variety of statistical quality control charts are used to monitor the output of a production process.
Economists use statistical information in making forecasts about the future of the economy or some aspect of it.
Stock Annual Earn/
Company Exchange Sales($M) Sh.($)
DataramAMEX73.10 0.86
EnergySouth OTC74.00 1.67
Keystone NYSE 365.70 0.86
LandCare NYSE 111.40 0.33
PsychemedicsAMEX17.60 0.13
Observation
Variables
Elements
Data Set
Datum
Numerical data
Qualitative
Quantitative
Data Types
Levels of Measurement
Nominal
Ordinal
Ratio
Interval
Discrete
Discrete or continuous
Types of Data
Students of a university are classified by the school in which they are enrolled using a nonnumeric label such as Business, Humanities, Education, and so on.
Alternatively, a numeric code could be used for the school variable (e.g. 1 denotes Business, 2 denotes Humanities, 3 denotes Education, and so on).
Students of a university are classified by their class standing using a nonnumeric label such as Freshman, Sophomore, Junior, or Senior.
Alternatively, a numeric code could be used for the class standing variable (e.g. 1 denotes Freshman, 2 denotes Sophomore, and so on).
Melissa has an SAT score of 1205, while Kevin has an SAT score of 1090. Melissa scored 115 points more than Kevin.
Melissa’s college record shows 36 credit hours earned, while Kevin’s record shows 72 credit hours earned. Kevin has twice as many credit hours earned as Melissa.
Example: Hudson Auto Repair
The manager of Hudson Auto would like to have
a better understanding of the cost of parts used in the
engine tune-ups performed in the shop. She examines
50 customer invoices for tune-ups. The costs of parts,
rounded to the nearest dollar, are listed below.
Parts Percent
Cost ($)FrequencyFrequency
50-59 2 4
60-69 1326
70-791632
80-89 714
90-99 714
100-109 510
Total 50 100
18
16
14
12
Frequency
10
8
6
4
2
Parts
Cost ($)
50 60 70 80 90 100 110
Statistical Inference
1. Population
consists of all
tune-ups. Average
cost of parts is
unknown.
2. A sample of 50
engine tune-ups
is examined.
3. The sample data
provide a sample
average cost of
$79 per tune-up.
4. The value of the
sample average is used
to make an estimate of
the population average.
Population (all votes cast)
Sample (selected votes for observation)
Population Verses a Sample
Basic Definitions
collection and description of data