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**

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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**

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

**Relative frequency**

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*  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?**

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* 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