2. Measures of location and spread

Question 1

What is the mode?

Answer 1

The value that occurs most often

Question 2

What is the median?

Answer 2

The middle value when the data values are put in order

Question 3

What is the mean? How do you calculate it?

Answer 3

The average value

Mean = sum of values / number of values

Question 4

What is the equation for mean?

What is the equation for the mean using data from a frequency table?

Answer 4

See card

Question 5

What are quartiles in relation to measures of location?

Answer 5

Q3, Upper quartile: 75%
Q2, Median: 50%
Q1, Lower quartile: 25%

Question 6

What are percentiles?

Answer 6

They split the data set into 100 parts

Question 7

How do you calculate the quartiles?

Answer 7

Q1 = n / 4
Q2 = n / 2
Q3 = 3n / 4
This is called interpolation. This assumes that the data is evenly distributed

Question 8

What is the variance?

Answer 8

A measure of the spread of data

Question 9

What is the equation for variance?

Answer 9

See card

Question 10

What is the equation for standard deviation?

Answer 10

Square root of the variance

Question 11

What is the equation for variance and standard deviation for grouped data in a frequency table?

Answer 11

See card

Question 12

How do you decode data?

Answer 12

Variance: calculate the variance from the coded data, input the coded variance into the coding the rearrange to find the original variance
Standard deviation: same as variance, when you input the coded S.D, do not add or subtract anything

Question 13

What is a decile?

Answer 13

A tenth of the population

Question 14

How do you find Q1, Q2 or Q3 in a frequency table?

Answer 14

Start of group + ( (Position - number used so far) / group total ) X class width