Descriptive statistics Flashcards
1
Q
Measures of central tendency
A
- mean, median and mode
- describes data set with one value that represents center or middle of distribution
2
Q
Properties of mean
A
- uses all values of the data
- used in computing other statistics => variance
- sensitive to outliers! low or high extreme pulls it towards that value
3
Q
Properties of median
A
- used to find the center, or middle value of data set
- not sensitive to outliers
- used when needed to find out whether the data values fall into upper half or lower half of the distribution
4
Q
Properties of mdoe
A
- find out most (e.g. case) frequent
- when the data is categorical (nominal)
- the mode may exist or not, and there can be more than one
5
Q
What are the levels/scales of measurement?
N
O
I
R
A
nominal
ordinal
interval
ratio
6
Q
EXPLAIN noir
A
n: a label => gender, participant no., etc…
o: there is an implied order => rating scale
i: distance between each interval is equivalent => temperature
r: has true meaningful absolute zero => weight, height, etc…
7
Q
What are the measures of variability / dispersion?
A
- range
- standard deviation
- variance
8
Q
What do the V / D measures do?
A
- how spread out the data is
- how far away is the value (X) from the mean or median?
9
Q
Central tendency VS variability
A
C.T: how scores in a distribution congregate around the middle of the distribution
Variability: how spread out the scores are ALONG the distribution
10
Q
Range
A
- highest - lowest
=> sensitive to extreme outliers (alike the mean)
11
Q
Variability
low vs high
A
low = curve is narrow
high = curve is wide
12
Q
Variance
A
- average sum of the squared deviation scores from the mean
- the variance in a sample reflects the population using (n-1)
13
Q
SD
A
- square root of the variance
- how far the value deviates from the mean
14
Q
What is the z-score?
A
- the distance the score is from the mean, which is expressed in SD units
