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Flashcards in Statistics formula Deck (33):
1

What is the formula for standard deviation?

Sqrt(Sxx / n-1)

2

What is sxx?

(X1-meanx)^2 + (X2-meanx)^2+...+(Xn-meanx)^n
- Sigmax^2 - nxbarsqaured

3

What is variance?

S^2 so sxx/n-1

4

When do you use n and when do you use n-1?

1. For a full population, n
2. For a sample, n-1 (usually this)

5

How do you work out the probability of (AnB) if they are independent?

P(AnB) = P(A) x P(B)
Independent means with replacement

6

How do you work out the probability of (AnB) if they are mutually exclusive?

P(AnB) = 0

7

How do you work out (AuB) regardless if they are independent or mutually exclusive?

P(AuB) = P(A) + P(B) - P(AnB)

8

How do you work out P(AIB) always? And Independent? And mutually exclusive?

P(AIB)= P(AnB) / P(B)
If independent t it is just P(AIB) = P(A) since the P(B) cancels out
If mutually exclusive P(AIB) = O as you are dividing O by something

9

How do you always work out P(AnB)?

P(AnB) = P(BIA) x P(A)

10

What is the linear coding for Fahrenheit and Celsius?

F = 9/5C + 32
C = 5/9(F-32)

11

How do you calculate outliers?

-Data which is more than 1.5 x IQR
-Q1 - 1.5xIQR
-Q3 + 1.5xIQR
-mean - 2xsd
-mean + 2xsd
-If test scores, include all outliers (distribution continuous) except zeros where the candidates did not take the test)
-If not include say why bad experiment, taking a joke

12

How do you do quartile?

Look at notes

13

How do you work out mean?

sigmax/ n

14

How do you find IQR of even set of numbers?

-Split down middle
-Odd number on both sides
-Find middle position number of both

15

What is msd? (Mean squared deviation)

sxx / n

16

What is rmsd? (Root mean squared deviation)?

sqrt ( sxx / n )

17

What is the modal group? What is mode? What is bimodak?

-The range where the large promotion of the sample are in and it is the group with the most members
-The single value is called the mode
-If a second peak, even if one frequency is higher than the other
-Look at notes

18

What is the skew if the hump is closest to the y axis?

Positive Skewness

19

What is the distribution is the hump is further from the y axis?

Negative skewness

20

What is frequency density?

frequency / class width

21

Which boundary do you plot of cumulative frequency?

Upper boundary

22

When do you use a vertical line graph?

-Used to illustrate discrete data
-The scores can only take integer values
-Y axis is labelled frequency

23

How do you work out the median of any data?

The median Q2 is the value of the n+1 / 2 th item of data

24

What are the four measures of central tendency?

Mean, median, mode and midrange

25

If A and B are independent then P(BIA) is?

P(B)

26

If A and B are dependant then P(BIA) is?

- not P(BIA’)
-P(BIA) = P(BnA) / P(A)

27

If A and B are dependent then what is P(AnB)?

P(A) x P(BIA)

28

If A and B are independent then what is P(AnB)?

P(A) x P(B)!

29

How do you work out P(B)?

P(B) = P(AnB) + P(A’nB)

30

How do you work out E(x)?

Sigma rP(x=r)
- r x P(x=r) all added
-also known as mu

31

How do you work out E(x^2) ?

Sigma r^2P(x=r)

32

How do you work out variance?

E(x^2) - mu^2

33

How else can you work out variance?

E([X-mu]^2)
Sigma (r-mu)^2 x P(x=r)