econ project

Describing Data

Decision Making and Data Everyday decisions are based on incomplete Information:  How much will I make when I graduate from college?

 Will the price of Facebook stock be higher in six months than it is now?

 Will interest rates remain low for the rest of the year if the budget deficit is as high as predicted?

Data are used to assist in decision making:

 Statistics involves the collection, presentation, and mathematical analysis of data.

 Key Statistical Terms:

 Population: collection of all items under investigation.

 Sample: subset of the population.

 Representative Sample: sample possessing similar characteristics to the population.

 Random Sample: occurs when there is an equal likelihood of choosing sample

members from a population.

 Parameter: a specific characteristic (data collected) of a population.

 Statistic: a specific characteristic (data collected) of a sample.

 Variable: a characteristic of interest from a population (denoted X or Y).

 Data: actual values that variables take on.

Collection & Presentation of Data

Data

Qualitative Quantitative

Discrete Continuous Marital Status

Nationality

Race

Gender

Sexual Orientation

# of Children

# of Voters

Weight

Age

Presenting Data

• Frequency Distribution Tables

• Column, Bar charts, and Histograms

• Pie chart

• Line charts and Scatter Plots

Proportional % of Smokers

% of Democrats

Frequency Distribution Tables

3 x 3 Cross Table (r x c) for Investment Choices by Investor (values in $1000’s)

Bar Charts & Histograms

Unlike a column graph, a histogram has no natural separation between rectangles of adjacent classes and always identifies frequency on the vertical axis.

Hospital Patients by Unit

Emergency

25%

Maternity

6%

Surgery

53%

Cardiac Care

12%

Intensive Care

4%

Pie Charts

(Percentages

are rounded to

the nearest

percent)

Hospital Number % of Unit of Patients Total

Cardiac Care 1,052 11.93

Emergency 2,245 25.46

Intensive Care 340 3.86

Maternity 552 6.26

Surgery 4,630 52.50

Line Charts and Scatter Plots

Ideal for

correlation and

Time-series data

Descriptive vs. Inferential Statistics

 Descriptive Statistics

 Collecting and presenting data.

 Inferential Statistics

 Drawing conclusions and/or making decisions about a population based only

on sample data.

 Why Sample? Less time consuming, less costly, and sufficiently precise.

Methods of Sampling • Simple Random: select such that any individual or group of individuals is equally likely to

be selected.

• Systematic: randomly select a starting point and take every nth data piece.

• Cluster (Area): divide the population into groups then randomly sample.

• Stratified: divide the population into groups then take a proportionate number form each

stratum.

• Convenience: non-random sampling done for efficiency purposes.

Excel Practice

 Use the “Store” Practice Data Set to to create one

horizontal bar chart for store 1, vertical bar chart

for store 2, and a histogram for store 3.

 Using the “Energy Price” Practice Data Set create

a time series line and scatter plot for gas prices.

 Using the survey monkey class data create a pie

chart illustrating the percentage of students

that……..