An Introduction to Statistics and
I. Two Branches of Statistics
A. Describe data
Descriptive Statistics: Organize,
summarize, and communicate a group of
B. Make inferences.
Chapter 2. Frequency Distributions
I. Frequency Distributions
Raw Scores: data that has not been analyzed yet.
Frequency Distribution: describes the pattern of a set of
numbers by displaying a count or proportion for each
possible value of a variable.
o Is a descriptive statistic that best represents the center of a data set
o Three measures:
Mean: Arithmetic average
Median: middle score
Mode: most common score
o Symbols for mean: M & X (with line above it)
o X: refers to s
Central Tendency and Variability
I. Central Tendency
Is a descriptive statistic that best represents the center of a data
Three measures of Central Tendency:
1. Mean: Arithmetic average.
2. Median: Middle score.
3. Mode: Most common score
Homework Assignment Chapter 1
1. The two branches of statistics are _ and _.
a. theoretical statistics; applied statistics
b. research design; data analysis
c. numerical methods; graphical methods
d. descriptive statistics; inferential statistics
Sampling and Probability
Two General Forms of Samples:
Random Samples every member of the population has an
equal chance of being selected.
Random Sampling is ideal but expensive, time-consuming and often
Convenience Samples uses
Raw Scores: Data that has not been analyzed yet
Frequency Distribution: describe the pattern of a set of numbers by displaying a count or
proportion for each possible value of a variable
Frequency Table: Displays counts for each value of one interval var