# 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
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