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……..