Y1, C2 - Measures of Location & Spread

Question 1

What are measures of location

Answer 1

Single values which describe a position in a data set

Question 2

What are measures of spread to do with and give examples

Answer 2

How data is spread out
e.g. range, variance, IQ range, standard deviation

Question 3

What are the measures of central tendency

Answer 3

Mode
Median
Mean

Question 4

What does x bar mean

Answer 4

The mean value of x

Question 5

What is the formula for the mean of ungrouped data

Answer 5

(Sum of the values * frequencies) / (sum of the frequencies)

Question 6

What is the formula for the mean of grouped data

Answer 6

Find the midpoint of each group and assign to x (assume all values are the midpoint value)
(Sum of the values * frequencies) / (sum of the frequencies)

Question 7

What type of data can’t a calculator find the IQ ranges for

Answer 7

Grouped data

Question 8

What does the median ignore

Answer 8

Extreme values

Question 9

What is the median

Answer 9

The middle value of data

Question 10

How to find the median of ungrouped data

Answer 10

n / 2
Where n is the number of items
If a decimal, round up
If a whole number, half way between this item and the one after

Question 11

How to find the median of grouped data

Answer 11

n / 2
Use linear interpolation

Question 12

What is the class width of: Weight of cat to the nearest kg 10 - 12

Answer 12

3
9.5 <= w < 12.5

Question 13

How to find upper and lower quartiles

Answer 13

1n/4 or 3n/4
Where n is the number of items
If a decimal, round up
If a whole number, half way between this item and the one after

Question 14

Notation for quartiles, median, deciles and percentiles

Answer 14

Q1
M / Q2
D3 / P30
P25 / Q1

Question 15

How to calculate IQ range

Answer 15

Q3 - Q1

Question 16

What is the variance

Answer 16

A measure of spread which takes all values into account
The average squared distance from the mean

Question 17

Formula for variance of ungrouped data

Answer 17

Sum of squared distance from the mean / number of values
OR
(Sum of the values squared / number of values) - mean squared

Question 18

What is standard deviation

Answer 18

The square root of variance

Question 19

What is the average distance from the mean called

Answer 19

The standard deviation

Question 20

What parts of coding affect measures of spread

Answer 20

Only multiplicative parts

Question 21

Which parts of coding affect measures of location

Answer 21

All parts of coding

Question 22

What is the formula for linear interpolation to find the median of cumulative data

Answer 22

Median = start value + (fraction from top) x class width)
Where if the frequency was 55 to 100 and you were finding the 75th position, the fraction from top would be 20 / 45