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