1. Elementary Applied Statistics
Kathy Ensor, Chair
Department of Statistics

2. What is Statistics?
“Statistics is the science of collecting, organizing, and interpreting numerical facts, which we call data”. Pg xxv
Based on a “representative sample” what can we say about the population of interest?
Use of statistics is pervasive in our society.
Examples?

3. Data? Numerical facts? Numerical summaries of what?
Sampling unit - the object or individual on which we are taking a measurement
Sampling frame or population - the group from which the sampling units are selected
Variable - the characteristic of the sampling unit that we measure

4. Categorical Variable
The sampling unit belongs to one of several groups.
Examples? - time for you to speak up!
Nominal - No ordering to the categories (blue, red, green, yellow)
Ordinal - there is a natural ordering to the categories (excellent, very good, good, …)

5. Quantitative variable
Numerical measures of a variable
Examples?
Arithmetic operations make sense (adding, dividing…)
Ratio and interval scales

6. Distribution A variable can take on a range of values.
The values do not occur in equal numbers
“The distribution of a variable tells us what values it takes and how often it takes these values.”
Variables exhibit variation; the distribution is the pattern of this variation

7. Displaying Distributions with Graphs
Categorical data
Pie charts
Bar charts
A plot of the count for each category of the variable.
What information can you glean from these graphs? Which is the better of the two?

8. Quantitative Variables
Stemplots (stem and leaf plot)
Back to back stem and leaf plot
describing two variables.
Histogram
frequency or relative frequency of the number of values of the variable falling into the specified interval.