INTRO+DATASETS

Question 1

What is Data Science

Answer 1

process of building, cleaning, structuring datasets to analyse and extract meaning

Question 2

Process of Data Science

Answer 2

1. Ask interesting qn
2. Get data
3. Explore data
4. model data
5. visualize and communicate results

Question 3

key principles in DS

Answer 3

• get many data sources
• understand how data collected
• use statistical models
• understand correlations
• good comm skills

Question 4

What does the discussion of probability include

Answer 4

-random experiments that produce a series of possible outcomes (can be infinity outcomes)

Question 5

elements of probability model (uncertainty of experiment)

Answer 5

• sample space(ohm symbol)(set that contains all possible outcomes. outcomes are mutually exclusive and collective exhaustive)(an event is a collection of one or more outcomes–subset of sample space)
• probability fraction p(A) assigns event A a no. between 0 and 1. Complement of event A= A^c– p(A^c)=1-p(A)

Question 6

conditional probability

Answer 6

probability of outcome A given that event B (DENOMINATOR)has occurred.

Question 7

independent

Answer 7

A and B are independent if the occurrence of B provides no information about A. intersect of events A and B =P(A)*P(B)

Question 8

Variable?

Answer 8

variable is any characteristic observed in a study. summary of ALL outcomes in a random process

Question 9

quantitative variable

Answer 9

there is meaningful distance between any 2 points of data

Question 10

types of categorical variable

Answer 10

• ordinal

- nominal

Question 11

types of quantitative variable

Answer 11

• discrete (separate numbers)

- continuous (possible values form an interval)

Question 12

distribution of a variable (probability distribution)

Answer 12

list of possible outcomes+associated probability

Question 13

Cumulative probability distribution

Answer 13

probability that the discrete variable is less than or equal to a particular value.

Question 14

probability density function (used for continuous variable as impossible to list down all values and prob for each value

Answer 14

Probability density function (PDF) is the probability that the value of a continuous variable falls within an interval.

Question 15

cumulative density function

Answer 15

Cumulative distribution function (CDF) is the probability that the variable is less than or equal to a particular value.

Question 16

modal category?

Answer 16

category with the highest frequency

Question 17

Bar plot (common way to display categorical variable)

Answer 17

One vertical bar for each possible category that could occur,
with the height proportional to the frequency of that category.

Question 18

Histogram(quantitative variable)

Answer 18

• Divide the range of data into intervals of equal width.
• Count the number of observations that fall within each interval.
• Label the intervals on the x-axis.
• Draw a bar over each interval

Question 19

Weakness of range?

Answer 19

sensitive to extreme observations

Question 20

variance definition

Answer 20

average squared deviations from the mean

Question 21

empirical rules of SD

Answer 21

• 68% of observations fall within +-1SD
• 95% fall within +-2SD
• almost all fall within +-3SD(check for outliers)

Question 22

interquartile range

Answer 22

range between upper and lower quartiles (robust to outliers)

Question 23

5 number summary

Answer 23

min , lower quartile, median (X0.5), upper quartile, max (min N max NOT considering outliers)

Question 24

when does an association exist?

Answer 24

if a particular value for a certain variable(response/dependent) is more likely to occur with certain values of another variable(explanatory/independent)

Question 25

covariance

Answer 25

measures the extent to which two variables move in the same direction

Question 26

correlation

Answer 26

covariance between two variables divided by the product of their standard deviations

Question 27

To check your working directory

Answer 27

getwd()

Question 28

get data types

Answer 28

class(a) (if a assigned to smth)

Question 29

true or false class?

Answer 29

logical

Question 30

Creating a vector of numbers and name it x

Answer 30

x=c(1,2,3,4) x= 1 2 3 4 class:numeric

Question 31

length of vector

Answer 31

length(x)

Question 32

alternative ways to write | x = matrix(c(1, 2, 3, 4), nrow = 2, ncol = 2)

Answer 32

x=matrix(c(1,2,3,4),2,2) | x=matrix(1:4,2,2)

Question 33

vector by row first?

Answer 33

y=matrix(1:4,2,2,byrow=TRUE)

Question 34

class of matrix?

Answer 34

'matrix' 'array'

Question 35

dimension of matrix

Answer 35

dim(x)=2 2 (row then column)

Question 36

extract component from row 2, column 3 of matrix A

Answer 36

A[2,3]

Question 37

attain subset of first row of A

Answer 37

A[1,]

Question 38

delete first row of A

Answer 38

A[-1,]

Question 39

list out all objects?

Answer 39

ls()

Question 40

remove one or all object?

Answer 40

- rm(x) | - rm(list=ls()) (must contain name or character strings)