3. Summarising and analysing data - 2

Question 1

Arithmetic mean

Answer 1

x̄ = Σx / n x = variable n = number of values of x

Question 2

Arithmetic mean on frequency distribution

Answer 2

x̄ = Σfx / Σf f = frequency x = variable

Question 3

How to work out the mean on grouped frequency distribution

Answer 3

Find the mid point for x x̄ = Σfx / Σf

Question 4

Median

Answer 4

the middle number if there is an even number of items take the two middle items and divide by 2 to give you the median

Question 5

Mode

Answer 5

Most often occurring number

least useful function

Question 6

Measures of spread

Answer 6

the range standard deviation the variance the coefficient of variation

Question 7

The range when arranged in classes

Answer 7

the highest value minus the lowest value

Question 8

The range when data is not grouped

Answer 8

the highest value minus the lowest value + 1

Question 9

Standard deviation

Answer 9

measures how far away from on average the data points are from the mean

Question 10

Standard deviation formula

Answer 10

Question 11

the coeffiecient of variation

Answer 11

standard deviation

/

mean

is useful when comparing the degree of variation from one data series to another, even if the means are quite different