PSY 411 Chapter 2 Notes

Bar graph

• A representation of a frequency distribution, where vertical bars are centered above each category along the x-axis and are separated from each other by a space, indicating that the levels of the variable represent distinct, unrelated categories

Class Interval Frequency Distribution

• simplifies frequencies further using bins, but at the expense of losing information

Frequency

• How often values appear in the data

Frequency Distribution

• A table in which all of the scores are listed along with the frequency with which each occurs

Frequency Polygon

• A line graph of the frequencies of individual scores

Histogram

• A graphical representation of a frequency distribution, in which vertical bars centered above scores on the x-axis touch each other to indicate that the scores on the variable represent related, increasing values

Qualitative Variable

• A categorical variable for which each value represents a discrete category

Quantitative Variable

• A variable for which the scores represent a change in quantity

Descriptive statistics

• Numerical measures that describe a distribution by providing information on the central tendency of the distribution, the width of the distribution, and the shape of the distribution

Mean

• arithmetic average of a group of scores

Measure of central tendency

• A number intended to characterize an entire distribution focused on  “middleness” 

Median

• middle score after scores are arranged from highest to lowest

Mode

• the score in a distribution that has the greatest frequency

Range

• A measure of variation; the difference between the lowest and the highest scores in a distribution

Apparent limit

• Scores: Simplifies frequencies further using bins 

Exact/real limit

• the lower or upper value for a continuous variable measured on a ratio scale
• above and below frequencies

Relative frequency

•  gives you sense of weighting/ how much of total group are we seeing 
• - should equal to around 1

Relative frequency %

• Turning the relative frequency into percentage
• total should equal 100

Midpoint

• Middle value of apparent limit

Cumulative frequency

• adding above and below frequency value

Cumulative frequency %

• turning the cumulative frequency into percentage

Key Concepts

What are the benefits of examining and visualizing frequency data?

• Can point to different characteristics of our sample (rare or common responses) 
• Help us find errors