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Stats 315 > 3-Properties of distributions > Flashcards

3-Properties of distributions Flashcards

1
Q

What is a central tendency?

A

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

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2
Q

What are the three most common central tendencies?

A

Mean, median and mode

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3
Q

What does this symbol (Σ) means?

A

It means the sum (capital S in greek)

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4
Q

1)What does this formula is used for ?:

m= (Σy)/n

2) What does every letters mean?

A

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

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5
Q

What are Greek symbols and Roman characters used for respectively?

A

1) Greek : parameters

2) Roman : statistics

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6
Q

What does this symbol µ means ?

A

The mean of a population

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7
Q

What is the median ?

A

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

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8
Q

What is the formula to find the median position?

A

Median position = (n+1)/2

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9
Q

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

A

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

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10
Q

What is the mode ?

A

The most occuring score in a set

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11
Q

What is the main difference between the mean and median?

A

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.

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12
Q

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

A

The mode

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13
Q

What does dispersion stands for ?

A

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

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14
Q

What is an outlier?

A

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

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15
Q

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

A

True, if the outliers are judged invalid

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16
Q

What are the three most used measures of dispersion?

A

The range, variance and standard deviation

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17
Q

How do you calculate the range?

A

Max-min

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18
Q

True or false. The range is highly sensitive to outliers

A

True

19
Q

What is the variance ?

A

The mean squared deviation from the mean

20
Q

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

A

The variance (mean squared deviation from the mean)

21
Q

What is the formula for variance in a POPULATION ?

A

σ2= S(y-mew)^2/N

so every score in y - mew

22
Q

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

A

The difference between a score and the mean

y-mew

23
Q

What is the formula for variance in a SAMPLE:

A

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

24
Q

What is the standard variation ?

A

The square root of the variance

25
Q

What is the formula for standard variation in POPULATION?

A

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

26
Q

What does the symbol σ stands for ?

A

Standard variation

27
Q

What is the formula for standard deviation in a SAMPLE:

A

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

28
Q

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

A

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

29
Q

What is another formula to calculate the sample variance?

A

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

30
Q

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

A

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

31
Q

How would you report statistics of mean and standard deviation ?

A

M=

s=

32
Q

What does the error bars represents in a graph ?

A

It represent the variability

33
Q

What is the shape of a distribution ?

A

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

34
Q

What is a normal distribution ?

A

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

35
Q

What are non-normal distribution called ?

A

Skewed distribution

36
Q

What are right skewed and left skewed also called ?

A

Right: Positively skewed

Left : Negatively skewed

37
Q

What is the consequence of left and right skewed ditribution

A

1) Right : floor effects

2) Left: ceiling effects

38
Q

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

A

Positive

39
Q

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

A

The mean is going to be above the median

40
Q

What is kurtosis ?

A

The sharpeness of the peak of a probability distribution

41
Q

How do you call a normal kurtosis ?

A

mesokurtic

42
Q

How do you call a kurtosis with sharp peak ?

A

leptokurtic

43
Q

How do you call flat kurtosis?

A

platykurtic

44
Q

What are multimodal distributions?

A

Distributions with more than one peak

Stats 315 (11 decks)

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