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Definition
| Summarizes data numerically and graphically, using descriptive statistics and graphs. |
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| Makes statements about some feature of the population (parameter) after analyzing the data. |
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| Measurement scales (or level of measurement) |
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| Classification that describes the nature of information within the values assigned to variables. |
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| Four measurement scales (list them in increasing order) |
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Definition
1. Nominal (lowest - has the least amount of information)
2. Ordinal
3. Interval
4. Ratio (highest - has the most amount of information) |
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| Nominal variables have no inherent order. They are values to distinguish categories, such as gender (male/female) or race/ethnicity (white/black/AA/Asian). |
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Values are ranked to give an order, but the level of difference between ranks is not constant.
Likert Scale is common, such as when you rank something from bad to fair to good. |
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Definition
Continuous variables, with a true distance between values that are equally spaced.
Zero is arbitrar, because it could be Fahrenheit or Celsius.
An example of an interval scale is measuring temperatures, with 1 degree, 2 degrees, 3 degrees, etc. |
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Definition
Ratio scale is a continuous variable. It has equally spaced intervals.
It has an absolute zero.
For example, if we measure height, zero means the same thing always.
Note that this is a scale, not a ratio! |
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There is a fixed number of outcomes (nominal, like gender or race).
A categorical variable with exactly two outcomes is a dichotomous variable. |
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Definition
| Can also be called categorical. It has a fixed number of outcomes, but is on an ordinal scale, so it has categories of inherant order (ie, socioeconomic statuses of low, medium, and high). |
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Term
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Definition
| It's usually on an interval or ratio scale. It can have any defined value, between a minimum and maximum. For example, your GPA can be any number between 0 and 4.0. |
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Definition
| Counts of categories; can be presented in a table or bar chart. |
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| Percentages of categories; can be presented in a bar chart or a table. |
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Definition
What happens in the "center" of the population? What is the typical value for the population?
Uses mean, mode, and median |
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| How do we summarize categorical and ordinal variables? |
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Definition
| With frequencies or relative frequencies, on a bar chart or table. |
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| Middle value of the sample; also called "the second quartile" |
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Definition
How spread out your values are in the population; opposite of central tendency.
Uses standard deviation, variance, range, and interquartile range. |
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Definition
Spread from the mean in original units --
how far are your observations from the mean? |
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Definition
| Spread from mean in squared units. |
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Definition
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| Interquartile range (IQR) |
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Definition
| 3rd minus 1st quartile (what's the spread in the middle?) |
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| How do we graph continuous variables? |
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Definition
| Histograms, which help you determine the shape of the data. |
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Definition
| Mean and median are the sam |
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Definition
Mean is greater than median;
picture is high to low |
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Definition
| Mean is less than median; picture is low to high |
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