Flashcards in Key knowledge for statistics Deck (18):

1

## Is the product moment correlation coefficient affected by coding?

### No

2

## How do you prove independence in probability?

###
P(A) x P(B) = P(AnB)

or

P(AIB) = P(AnB)/P(B) = P(A)

3

## In probability if the variables are mutually exclusive what is the value of P(AnB)?

###
P(AnB) = 0

so

The addition formula will be

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

4

## When you have to work out the mean of data before it was coded, what do you do?

###
Find the mean of the coded data, then make the mean equal to the coded formula and solve.

For example if you worked out the mean of the coded data to be 3, and the coding used was y = (x-100)/10

make (x-100)/10 = 3, then solve

mean of data without coding = 130

5

## When working grouped frequency distributions (eg. tables that include class such as 12 < x < 13), What do you need to include when working out class width?

###
The upper and lower bounds.

Eg.

LB= 11.5

UB = 13.5

6

## The height of a bar in a histogram is referred to as?

### Frequency density

7

##
If you have data such as

group:2 ≤ x ≤ 4 frequency: 7

how would you work out ∑fx?

###
You need to find the midpoint of x (in this case it would be 3) then times it by the frequency.

So ∑fx = 3 x 7 = 21

8

##
If you have data such as

group:2 ≤ x ≤ 4 frequency: 7

how would you work out ∑fx^2?

###
You need to find the midpoint of x (in this case in would be 3) square it , then times it by the frequency.

So ∑fx^2 = (3)^2 x 7 = 63

9

##
If you had to work out ∑fx^2 with data

x = 2 frequency = 5

what would you do?

###
You square the x value and times it by the frequency.

So ∑fx^2 = (2)^2 x 5 = 20

10

## In coding does adding or subtraction affect the standard deviation of the data?

### No

11

## In coding does multiplication or division affect the standard deviation of the data?

###
Yes.

For example if the SD of the coded data is 3 and the coding formula used was y = x/10, then the SD of the data without coding would be 3 = x/10 => x = 30.

12

## In a histogram what is the area of the bar proportional to?

### Frequency

13

## In probability what must everything in total equal?

### 1

14

## How would you work out the P(A')?

### 1 - P(A)

15

## In correlation, if r = 1 what can you state about the data?

### It has a perfect positive correlation.

16

## In correlation, if r = 0 what can you state about the data?

### It has no correlation.

17

## In correlation, if r = -1 what can you state about the data?

### It has a perfect negative correlation.

18