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 central tendency, width and 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

Midpoint

Middle value of apparent limit

Cumulative frequency

adding above and below frequency value

Cumulative frequency %

turning the cumulative frequency into percentage

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

Identifying and correcting misleading graphs

• Dates out of order

• No y axis

• Missing axis labels

• Make sure y axis starts at 0