Aantekeningen Beschrijvende en Inferentiële Statistiek
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Course
Beschrijvende en Inferentiële Statistiek
Institution
Vrije Universiteit Amsterdam (VU)
Dit is een samenvatting van de colleges en de kennisclips van Beschrijvende en Inferentiële Statistiek bij de VU. Alle stof van module 0 tot 13 komt hier aan bod. Ik had een 7 voor dit tentame.
Termen
Werkcollege 1 (7/2/2023)
Type variabelen:
Categorisch (nominaal en ordinaal): Variabelen zoals lievelingskleur. Je kan er niet echt mee rekenen.
Nominal: when it has a noun, like someone's hair colour. You need a name for it.
Ordinal: Involves arranging numbers. it's organised, if something is on a scale of 1-5, 3 will never be an
extreme value.
Kwantitatief (discreet en continu): Getallen waar we mee kunnen rekenen.
Continuous: A continuous scale of something, like temperature. Like a gay person with a partner.
Discreet: Something that is not connected. Imagine like someone with internal homophobia, they're always
alone.
CALCULATING PERCENTAGES
Deel/geheel x 100
If change: new/old x 100
Verdeling van de data (data distribution):
● Uni-/ bimodaal
● Scheefheid
● Normaalverdeling (“bell shape”)
Grafiek, grafische weergave:
Categorisch
● Pie chart (taartdiagram); bar chart (staafdiagram)
Kwantitatief
● Histogram; stem-and-leaf plot; dot plot; box plot
Centrummaten:
Mode
● Value that occurs most frequently.
● Often used if a variable is measured on a nominal or ordinal level.
● You can have more than one mode.
Median
● Middle value of your observations when arranged from the smallest to the largest.
● When you have an even number of cases take the average of the middle numbers.
,Mean
● Sum of all the values divided by the number of observations.
Bij een left skewed graph:
1: Mean.
2: Median.
3: Mode.
Spreiding:
● Standaarddeviatie
● Variantie
● Range
● Interkwartielafstand (IQR)
Range
● Difference between the highest and lowest value.
● Subtract the lowest from the highest number to find.
● Advantages: Easy to understand, simple to compute.
● Disadvantages: Doesn't give a good impression of the variability, only takes into account the
extreme values.
, Interquartile range
Leaves out the extreme values. Divides a graph in four
equal parts. These are called quartiles. Q2 is the
median. The interquartile range is the distance
between the third and the first quartile.
Q2 = median
Q1= middle value left side of median
Q3= middle value right side of median
IQR= Q3 – Q1
Variance
Σ(𝑥−𝑥̄)
s2= 𝑛−1
S2: Variance
(x - x̄): From every observation (x) you have to subtract the mean variable (x̄), square all these values and add
them up. This result is the sum of squares.
N - 1: Divide the sum of squares with the sample size (n) - 1.
Disadvantage to using variance: the metric of the variance is the metric of the variable under analyses
SQUARED.
Standaarddeviatie
De standaarddeviatie geeft aan hoeveel de data Gemiddeld afwijkt van het gemiddelde.
Voor uitrekenen:
● Je kijkt eerst naar hoeveel elke observatie van het gemiddelde afwijkt.
X - x̄
●
● Standaarddeviatie zegt dus iets over de spreiding. Dit zegt iets over de zekerheid.
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