3-Properties of distributions

Question 1

What is a central tendency?

Answer 1

The summarization of a score distribution by providing a single number. This number is called an average

Question 2

What are the three most common central tendencies?

Answer 2

Mean, median and mode

Question 3

What does this symbol (Σ) means?

Answer 3

It means the sum (capital S in greek)

Question 4

1)What does this formula is used for ?:

m= (Σy)/n

2) What does every letters mean?

Answer 4

1) This formula is to calculate the mean in a sample
2) m: mean
Σy: The sum of all the scores in y : every score
n: The numbers of scores

Question 5

What are Greek symbols and Roman characters used for respectively?

Answer 5

1) Greek : parameters

2) Roman : statistics

Question 6

What does this symbol µ means ?

Answer 6

The mean of a population

Question 7

What is the median ?

Answer 7

A number that seperates an ordered set of number in two groups of equal size

Question 8

What is the formula to find the median position?

Answer 8

Median position = (n+1)/2

Question 9

What happen with even numbers of scores for finding the median?

Answer 9

The median position will be between two scores, so we will do the average of those two scores.

Question 10

What is the mode ?

Answer 10

The most occuring score in a set

Question 11

What is the main difference between the mean and median?

Answer 11

All scores are used with the mean. If one if removed, it is going to change. In the median, only a few scores is gonna affect it, so if one is removed, it won’t change much.

Question 12

Between the mean, median and mode, what is the best for qualitative variables ?

Answer 12

The mode

Question 13

What does dispersion stands for ?

Answer 13

how spread out scores are in a distribution of a quantitative variable

Question 14

What is an outlier?

Answer 14

A score that is unusually far from the central tendency of the distribution.

Question 15

True or false. You can exclude outliers with the right justification

Answer 15

True, if the outliers are judged invalid

Question 16

What are the three most used measures of dispersion?

Answer 16

The range, variance and standard deviation

Question 17

How do you calculate the range?

Answer 17

Max-min

Question 18

True or false. The range is highly sensitive to outliers

Answer 18

True

Question 19

What is the variance ?

Answer 19

The mean squared deviation from the mean

Question 20

What does this symbol stands for : σ2 (sigma square) ?

Answer 20

The variance (mean squared deviation from the mean)

Question 21

What is the formula for variance in a POPULATION ?

Answer 21

σ2= S(y-mew)^2/N

so every score in y - mew

Question 22

What is the deviation score, and what is the formula ?

Answer 22

The difference between a score and the mean

y-mew

Question 23

What is the formula for variance in a SAMPLE:

Answer 23

s^2= S(y-m)^2/(n-1) or ss/(n=1)

Question 24

What is the standard variation ?

Answer 24

The square root of the variance

Question 25

What is the formula for standard variation in POPULATION?

Answer 25

o= squaroot of o^2=squaroot of S(y-mew)^2/N

Question 26

What does the symbol σ stands for ?

Answer 26

Standard variation

Question 27

What is the formula for standard deviation in a SAMPLE:

Answer 27

s= squareroot of s^2= squareroot of S(y-m)^2/(n-1)

Question 28

In words, what does the standard deviation means in a context?

Answer 28

It is roughly the average distance (deviation) of scores from the mean.

Question 29

What is another formula to calculate the sample variance?

Answer 29

s^2=s^2pop* (n/n-1)

Question 30

Why is the standard deviation more intuitive than the variance for measuring variability?

Answer 30

because it is more directly related to differences in variability between two sets of scores.

Question 31

How would you report statistics of mean and standard deviation ?

Answer 31

M= | s=

Question 32

What does the error bars represents in a graph ?

Answer 32

It represent the variability

Question 33

What is the shape of a distribution ?

Answer 33

How density (or frequency) changes as a function of the values of the variable.

Question 34

What is a normal distribution ?

Answer 34

When it is symmetrical with a single peak (mode) (unimodal)

Question 35

What are non-normal distribution called ?

Answer 35

Skewed distribution

Question 36

What are right skewed and left skewed also called ?

Answer 36

Right: Positively skewed | Left : Negatively skewed

Question 37

What is the consequence of left and right skewed ditribution

Answer 37

1) Right : floor effects | 2) Left: ceiling effects

Question 38

With the skew, if the tail goes towards the biggest possible score it is a negative or positive skew

Answer 38

Positive

Question 39

What is the position of the mean in a positively skewed distribution?

Answer 39

The mean is going to be above the median

Question 40

What is kurtosis ?

Answer 40

The sharpeness of the peak of a probability distribution

Question 41

How do you call a normal kurtosis ?

Answer 41

mesokurtic

Question 42

How do you call a kurtosis with sharp peak ?

Answer 42

leptokurtic

Question 43

How do you call flat kurtosis?

Answer 43

platykurtic

Question 44

What are multimodal distributions?

Answer 44

Distributions with more than one peak