About Data 1

Question 1

What are the rows and columns of the data table called?

Answer 1

Rows (observations/cases)

Columns (variables)

Question 2

What are the two sub classes of numerical variables and what do they mean?

Answer 2

Continuous - infinite choices

Discrete - finite choices

Question 3

What are the two categorical variable sub classes and what do they mean?

Answer 3

Ordinal - has natural order

Regular- doesn’t have natural order

Question 4

Associated vs independent variables?

Answer 4

Asssociated - two variables have a connection

Independent- no connection

Question 5

Anecdotal evidence?

Answer 5

Grandma says lightning cures cancer cuz it happend to her

Question 6

Problems with taking a census

Answer 6

Some are hard to locate
Complex
Population changes while cencus is being taken

Question 7

“Tasting soup” exploratory analysis, infrence and representative.

Answer 7

Exploritory analysis - gathering data (tasting the soup)
Inference - to generalize your claims to the whole population
Representative - does your sample represent tge whole population (it needs to!)

Question 7

Sampling bias from these- non response, voulentary response, convenience sample

Answer 7

Non response - if only a small fraction of randomly sampled people respond; the sample may no longer be representative of the population.
Voulentary response- only people who care to respond are those with strong opinions (npt representative)
Convineince sample- people who are more easily accessable are more likly to be in the sample

Question 8

Explanitory variable and response variables

Answer 8

Its a suggestion to which one is influencing the other (does not mean it is causal)

Question 9

Observational study

Answer 9

Data is collected in a way that does not effect how data comes “observes”

Question 10

Experiment

Answer 10

subjects are assigned treatments to establish causal connections between explanatory and response variables

Question 11

Co-founding variable

Answer 11

a variable which is correlated to the explanatory and response variables

Question 12

Two types of observational studys?

Answer 12

prospective and retrospective studys

Question 13

prospective study?

Answer 13

collects info as events unfold

Question 14

retrospective study?

Answer 14

collects info after events have taken place

Question 15

What are the four sampling methods?

Answer 15

simple random sampling
stratified “”
cluster “”
multistage “”

Question 16

Simple random sample

Answer 16

random samples

Question 17

Stratified sample

Answer 17

divides population into groups based on similar observations. Then takes random samples from each

Question 18

Cluster sample

Answer 18

divides population into random groups then takes whole cluster samples from some randomly chosen groups

Question 19

Multistage sample

Answer 19

make random clusters. then randomly chose clusters to sample. simple random sample within

Question 20

Principles of experimental design (4) C R R B

Answer 20

Control-compare treated with control group
Randomize- random samples
Replicate-do the experiment many times by collecting a large sample
Block-assign groups into subdivisions to eliminate a third variable

Question 21

Scatter plot

Answer 21

useful for visualizing the relationship between two numerical values

Question 22

Dot plots and mean

Answer 22

Shows the mean along with dots grouped densely up in a single line

Question 23

Sample statistic and point estimate

Answer 23

Sample statistic- data found from the sample

Point estimate- an estimation of the population

Question 24

Stacked plot

Answer 24

dots are piled on top of each other in multiple rows to show mean

Question 25

Histograms

Answer 25

shows data density, describes the shape of the data, bar width can alter the story (makes it less/more accurate) ex 1-10 vs 1-2

Question 26

4 types of histogram shapes

Answer 26

Uni modal - looks like normal distribution bimodal- two humps multi modal 3 or more humps uniform- one straight line

Question 27

3 types of skew

Answer 27

Right medianmean | symmetric median=mean

Question 28

Varience

Answer 28

``` average squared deviation from the mean. sum of(x-mean)^2/n-1 ```

Question 29

Standard deviation

Answer 29

sqrt (sum of(x-mean)^2/n-1 sqrt of variance all data should be within 3 sd's

Question 30

median

Answer 30

value that splits data in half when in ascending order. if even average of two mid #s

Question 31

Q1, Q3 and IQR

Answer 31

Q1=25th percentile median=50th Q3=75th percentile between Q1 and Q3 = the middle 50%= interquartile range=IQR

Question 32

box plot

Answer 32

represents the middle 50% with a box. with whiskers that can reach up to 1.5x the closest quartile. outliers are outside of the wiskers

Question 33

robustness | median and IQR vs mean and SD

Answer 33

median and IQR are more resistant to skewness. skewed distribution are rep by median and IQR. symmetric distribution rep by mean and SD

Question 34

Graph transformations

Answer 34

log(x) "eliminates outliers easier to model Hard to interpret

Question 35

contingency tables

Answer 35

summarizes data from two categorical variables

Question 36

bar plot

Answer 36

common way to show a single categorical variable

Question 37

histogram vs bar plot

Answer 37

histogram-numerical variables x axis number | bar plot-categorical variables x axis categories

Question 38

Segmented bar and mosaic plot

Answer 38

bar graph with legend. All the space is taken up to total # of samples with yes and no

Question 39

Pie charts

Answer 39

Don't use if comparing more than 5 items. Colorful but bad.