Study Notes #1

Descriptive Statistics

Data

Defined as distinct pieces of information and it can come in many forms.

Used to understand and improve things.

Data Types

  1. Quantitative – data takes on numeric values that allow us to perform mathematical operations (like the number of dogs).
    • Continuous – data can be split into smaller and smaller units, and still a smaller unit exists. An example of this is the age of the dog – we can measure the units of the age in years, months, days, hours, seconds, but there are still smaller units that could be associated with the age.
    • Discrete – data only takes on countable values. The number of dogs we interact with is an example of a discrete data type.
  2. Categorical – is used to label a group or set of items (like dog breeds – Collies, Labs, Poodles, etc.).
    • Ordinal – data take on a ranked ordering (like a ranked interaction on a scale from Very Poor to Very Good with the dogs).
    • Nominal – data do not have an order or ranking (like the breeds of the dog).

Summary Statistics

Measure of Spread – idea of how each data differ

Analyzing Quantitative Data

Four Aspects:

  1. Measures of Center
  2. Measures of Spread
  3. The Shape of the data
  4. Outliers

Measure of Center – idea of the average

Three widely accepted measures of center.

  • Mean=AVERAGE / sum of all the values in the data set divided by the count of values
  • Median – splits our data so that 50% of our values are lower and 50% are higher.
    1. Arrange the data set in order – lowest to highest value
    2. ODD count – the median is the middle value
    3. EVEN count – get the mean (average) of the two middle value
  • Mode
5, 8, 15, 7, 10, 22, 3, 1, 15
AVERAGE = 86/9 
MEAN= 9.56
5, 8, 15, 7, 10, 22, 3, 1, 15
1, 3, 5, 7, 8, 10, 15, 15, 22 = 9 COUNT
MEDIAN = 8
5, 8, 15, 7, 10, 22, 3, 1, 15, 2
1, 2, 3, 5, 7, 8, 10, 15, 15, 2 = 10 count
7+8 = 15/2
MEDIAN = 7.5

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