OpenIntro 2

Question 1

intensity map

Answer 1

colors are used to show higher and lower values of a variable

Question 2

contingency table

Answer 2

A data matrix that displays the frequency of some combination of possible responses to multiple variables; cross tabulation results

Question 3

mosaic plot

Answer 3

uses the area of rectangles to display the relative frequency of occurrence of all combinations of two categorical variables

Question 4

column proportions

Answer 4

computed as the count divided by the corresponding column total

Question 5

row proportions

Answer 5

computed as the counts divided by their row totals

Question 6

Dotplot

Answer 6

En-variabels scatterplot, bruges til at vise tendenser i enkelte variable fra datasæt. Prikkernes gennemsigtighed repræsenterer proportion (hvor mange lånrenter ud af alle er omkring 10%, eksempelvis) under dette er en trekant, der viser gennemsnittet, og under dette, værdier.

Question 7

stacked dotplot

Answer 7

Som et prikplot, men i stedet for gennemsigtighed som mål for hyppighed stables prikkerne så man får hele tal. Alt andet er ens. Virker naturligvis kun for relativt små datasæt, da man let kan løbe tør for plads.

Question 8

Mean vs median

Answer 8

Question 9

Median

Answer 9

Mellemste værdi i et SORTERET datasæt. Hvis n / 2 er et heltal (lige antal observationer), er den mellemste værdi gennemsnittet af de to mellemste værdier. Hvis ikke, er antallet ulige, og så vælger man bare den mellemste værdi. Repræsenterer centrum af et datasæt, og er mere robust end gns. (prøv at skrive et monsterstort eller småt tal i dine observationer, og se hvordan gennemsnittet ikke længere er repræsentativt). 50% af data over / større og 50% under / mindre end denne markør.

Question 10

Q1

Answer 10

Første kvartil (nederste / venstre side af boxplots “krop”) - Repræsenterer at 25% af værdier er under denne.

Remember: 50th interquartile range is the median

Question 11

Q3

Answer 11

Tredje kvartil (øverste / højre side af boxplots “krop”) - 75% af værdier under denne, eller 25% større end denne markør.

Question 12

Mean vs median

Answer 12

Question 13

modality and skewness

Answer 13

Question 14

Distribution

Answer 14

A function showing all possible values/intervals of the data & how often they occur.

Question 15

Data Density

Answer 15

The frequency of data at a certain value. Measured in a histogram.

Question 16

Mode/Unimodal/Bimodal/Multimodal

Answer 16

Question 17

Deviation

Answer 17

The distance of an observation from its mean.

Question 18

Standard Deviation

Answer 18

Measures how far the data are spread out from their average value.

Question 19

Sample Variance

Answer 19

Measures how far the data are spread out from their average value.

How wide is the distribution?

Question 20

Mode

Answer 20

In statistics, the mode is the one that occurs most.

Unlike the median and the mean, the mode is not necessarily unique. There might be several different values that occur the same number of times.

Question 21

Bar plot

Answer 21

For showing categorial data

(remember that a barplot can show “counts” or “proportions” in y axis

Question 22

Comparring nummerical data

Answer 22

Question 23

Null hypothesis vs alternative hypothesis

Answer 23

“there is nothing going on”

Question 24

Hypothesis test

Answer 24

Example using 100 simulations of the test, to make sure that there is or not is discrimination. One or two tests would most likely be down to chance alone, therefore you have to make a lot of simulations of the test.

1. “There is nothing going on.”
   Promotion and gender are independent, no gender
   discrimination, observed difference in proportions is simply due
   to chance. ! Null hypothesis
2. “There is something going on.”
   Promotion and gender are dependent, there is gender
   discrimination, observed difference in proportions is not due to
   chance. ! Alternative hypothesis

Question 25

cluster sampling

Answer 25

cluster sampling er den "fattige" stratified sample - vi vælger ikke selv grupperne, vi anter at fx lande eller klasser er gode nok til at skabe grupperne

Question 26

stratified sample

Answer 26

Stratification is the process of dividing members of the population into homogeneous subgroups before sampling. (svært at gøre og derfor er cluster sample nemmere)

Question 27

Ordinal vs not ordinal?

Answer 27

Ordinal data is a kind of categorical data with a scale to it. For example, ordinal data is said to have been collected when a responder inputs his/her financial happiness level on a scale of 1-10. In ordinal data, there is no standard scale on which the difference in each score is measured

Question 28

Skew vs mean, median

Answer 28

Right-skewed: mean \> median I Left-skewed: mean \< median