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).

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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