Task 2: The characteristic score.

Question 1

Statistic is

Answer 1

the science of learning from data.

Question 2

Data can be

Answer 2

Numerical and qualitative

Question 3

Cases are

Answer 3

the objects described by a set of data.

Question 4

A label is a

Answer 4

special variable used in some data sets to distinguish the different cases.

Question 5

A variable is

Answer 5

the characteristic of a case.

Question 6

Variables can be

Answer 6

Categorical (places the case into a group)

Quantitative (takes numerical values for which arithmetic operations make sense).

Question 7

Distribution of a variable tells us

Answer 7

what values it takes and how often it takes these values.

Question 8

Explanatory data analysis

Answer 8

Statistical tools and ideas that help us examine data to describe their main features.

Question 9

Categorial representations of a set of variables are

Answer 9

Bar graphs (more flexible) and pie charts (include all categories that make up a whole).

Question 10

Quantitative representations are made with the help of..

Answer 10

Stemplots (work better for small numbers that are greater than 0);
and
Histograms (columns don’t have spaces between them).

Question 11

Tails of the distribution contain..

Answer 11

the extreme values.

Question 12

The two principles of data examination:

Answer 12

1- plot your data

2- look for an overall pattern and any striking deviations.

Question 13

When examining a distribution, take the further three steps:

Answer 13

1- Overall patterns + striking deviations
2- Look at the shape (does it have modes = major peaks)
3- Is it symmetric? (mirror image)
4- Is it skewed? (skewed to the right if the right tail is longer)
5. Outliers.

Question 14

An outliers is

Answer 14

an individual value that falls outside the overall pattern.

Question 15

We can measure the centre with the help of:

Answer 15

The mean x(bar) and the median M.

Question 16

Characteristics of the mean.

Answer 16

• average value;

- is sensitive to the influence of outliers => NOT a resistant measure of the centre.

Question 17

Characteristics of the median.

Answer 17

• midpoint of a distribution;
• more resistant than the mean;
• typical. value.

Question 18

How to find the median?

Answer 18

1. arrange all obs. from the smallest to the largest.
2. (n+1)/2 = M
   that gives the location, not the actual mean.

Question 19

Methods for measuring spread:

Answer 19

1-Quartiles Q1 and Q3;

2- Standard deviation s

Question 20

To calculate Q1 and Q3:

Answer 20

1. Find the M.
2. Q1 (1/4 of the obs.) = the M of the observations whose position is to the left of the location of the overall M.
3. Q3 (3/4 of the obs.) = the M of those obs. that are located to the right of the overall M.

Question 21

The five-number summary consists of:

Answer 21

Minimum
Q1
M
Q3
Maximum.

Question 22

The interquartile range is used for describing..

Answer 22

skewed distributions.

Question 23

IQR =

Answer 23

Q3 - Q1

Question 24

The 1.5 x IQR is used for detecting

Answer 24

suspected outliers.

Question 25

Variance s2 is the..

Answer 25

average of squares of the deviations of the observations from their mean.

Question 26

Standard deviation s is the

Answer 26

square root of the variance.

Question 27

The sum of the deviations of the observation from their mean will always be..

Answer 27

0

Question 28

When there is no spread s =

Answer 28

0

Question 29

We only know s when we know the..

Answer 29

Mean.

Question 30

s is not

Answer 30

resistant.

Question 31

Linear transformations change…

Answer 31

the original variable x into the new variable x new.

Question 32

x new =

Answer 32

a + bx

Question 33

The characteristics of linear transformation are:

Answer 33

1. it does not change the shape of a distribution.
2. it changes the origin if a is not equal to 0.
3. if b > 0 => changes the size of the unit of measurement.