The Nature and Probability of Statistics
What is statistics?
The science of conducting studies to collect, organize, summarize, analyze and draw conclusions from data.
Two types of statistics:
1. Descriptive  collection, organization, summation & presentation of data
2. Inferential  generalizing, testing, determining relationships, making predictions, all from samples to populations  using probability theory
Some definitions:
Variables –mathematical symbols that represent a number,
but have no fixed value
Data  Value(s) that variables can assume (numbers, types, colors, etc.) Data set  A collection of data values Random Variables  Variables whose values are determined by chance Population  all data values being studied Sample  A subgroup of a given population

Questions
1. Give some examples of variables
a: Qualitative  can be placed into distinct categories: gender, color, religion
b: Quantitative  numerical, can be ordered or ranked: age, temperature, height
c: Discrete  assume values that can be counted (number of kids, days in a cycle)
d: Continuous  can assume all values between any two specific values (temp)
2. Boundaries  useful when considering continuous variables, allows us to more easily group them
Measurement Scales
1. Nominal: Classifies data into mutually exclusive categories in which NO order or ranking can be imposed on the data
1. Data collection techniques
a. Direct observations (should
be self explanatory)
b. Reviewing records (weather
temperatures over the last 50 years, etc.)
c. Surveys 
I. Telephone:
Advantages: cheap, people more candid w/o facetoface contact 
Disadvantages: Those w/o phones, those not at home or no answer 
II.
Mailed questionnaire:
Advantages: Cover a wider area, respondents anonymous 
Disadvantages: Low # of responses, incorrect reading of questions 
III.
Personal interview:
Advantages: Can get indepth responses 
Disadvantages: Interviewers must be trained (Q&A), expensive, interviewer may be biased in selection of respondents 
2. Sampling Techniques
a. Random  Selected by using chance methods or random numbers
b. Systematic  Numbering each subject of the population
and picking each kth number
(See page 12 for example need 50 out of 2000, every
40th w/1st picked at random)
c. Stratified  Divide population into groups according to some characteristic, then random sampling from each group (sample from freshmen, sophomores, juniors and seniors; sample from officers and enlisted personnel, etc.)
d. Cluster  Using intact groups that are representative of a population, such as the residents in a retirement home, kids in one school, nurses in a hospital
e. Convenience  Use subjects that are convenient
to study
Please Go to Lesson 2
