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Frequency Distributions

Quantitative distributions and histograms

Quantitative Variables

● Represent a measurable quantity

● Numerical

○ Number of credits taken fall semester

○ Pumpkin spice latte likability

● Can be meaningfully averaged,multiplied, divided and subtracted

Discrete vs Continuous

● Discrete variables

○ Countable number of value

○ Whole numbers- can you count it on your fingers ?

Examples: # of students in a class or correct answers on a tes

● Continuous variables

○ The unit of measure is divisible-a case could have any value in the unit

○ We can have decimals

Examples: Snowfall on Mt. Rose, GPA

Discrete or Continuous

● How many hipsters are in Bibo’s ? discrete

● What was your grade percentage on the first lab ? continuous

● How many cc’s of solution are in a syringe? Continuous

● How many accidents occur on 1-80 every week ? discrete

Visually Depicting discrete variables

● Frequency distributions are used to represent quantitative data

○ The easiest method is the frequency table

Visually Depicting Continuous Variables

● Histograms are visual representations of continuous quantitative data

● They are created by defining discrete intervals called bins (or classes)

● The height of each bin is equal to the frequency of cases in that particular bin

Histograms with Continuous Variables

● Given that our variable is continuous we have to find a way to group it

● To create a histogram

○ We create bins with an appropriate interval or step size

○ About bins:

■ The value you give is the upper limit of that interval

■ The bins must be exhaustive and mutually exclusive

■ Place the bins in the next column with a header (Bins)

Descriptive Statistics (measures of central tendency )

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