Exploratory Data Analysis and Data Visualization

Question 1

What are data sets made up of?

Answer 1

Data objects
i.e. medical dataset: patients, treatments, medicine

Database rows - data objects
Database columns - attributes

(also called samples, examples, instances, data points, objects)

Question 2

What are attributes in a dataset?

Answer 2

A data field representing a characteristic or feature of the data object
i.e. customer_ID

columns of the dataset

Question 3

What different attribute types do we know?

Answer 3

1. Nominal: Categories, states or names of things
   i. e. Hair-color = {black, blond, red, etc.}
2. Binary: Nominal attributes with only 2 states (0 and 1)
   i. e. gender, medical test
3. Ordinal: Values have a meaningful order (ranking) but magnitude between successive values in not known
   i. e. size = {small, medium, large} or army ranks

Question 4

What is the difference between discrete and continuous attributes?

Answer 4

1. Discrete attributes
   - Only a finite OR countable infinite set of values (zip codes)
   - binary attributes are a special case of discrete attributes
2. Continuous attribute
   - has real numbers as attribute values
   e. g. height, temperature, weight
   - usually represented as floating point variables

Question 5

What is the mean?

Answer 5

The average value of a dataset

calculated by the sum of all values divided by the number of values

Question 6

What is the median?

Answer 6

Middle value –> odd number of values

average of two middle values –> even number of values

Question 7

What is the mode?

Answer 7

Value that occurs the most frequently

Question 8

What is a Boxplot?

Answer 8

1. The end of the boxes mark the quartiles
2. The median is marked
3. The whiskers mark the outliers

Question 9

What does a Histogram display?

Answer 9

Graph display of tabulated frequencies , shown as bars

Question 10

What is the difference between bar chart and histogram?

Answer 10

Difference to bar chart: The bar denotes the value not the height

Question 11

What is a scatter plot good for?

Answer 11

Provides a look at clusters of points and outlier

Question 12

What interface do you use in python to visualize data?

Answer 12

pyplot interface of the matplotlibrary