Data processing, presentation and interpretation

Question 1

Outlier formulae

Answer 1

• Greater than Q3+1.5(Q3-Q1)
• Less than Q1-1.5(Q3-Q1)

Question 2

Ways of representing data

Answer 2

Box plots, cumulative frequency graphs, histograms

Question 3

Mean of values from frequency tables

Answer 3

mean= (total of (xf))/n
x= value of variable
xf= value of variable x frequency
n= number of data items (total frequency)

Question 4

Advantages and disadvantages of grouped data

Answer 4

+ Easier to display data
- Information is lost in the form of individual values, and therefore any measures calculated are only estimates

Question 5

Displaying continuous grouped data

Answer 5

Frequency charts, histograms

Question 6

Frequency charts

Answer 6

Used to display data that are grouped into classes of equal width

Question 7

Histograms

Answer 7

frequency density= frequency/class width
frequency density represented by y axis of histogram
frequency= area of bar

Question 8

Working out mean from grouped continuous data

Answer 8

mean= total of (mid-value x frequency)/total frequency

Question 9

What is the moral class in grouped continuous data

Answer 9

The highest bar of the histogram (highest frequency density)

Question 10

Cumulative frequency curves

Answer 10

• Plot upper bound of each class interval against cumulative frequency, then join points with smooth curve

Question 11

Bivariate data

Answer 11

Investigating the relationship between two variables

Question 12

Displaying bivariate data

Answer 12

Scatter graphs can be plotted and then correlation (strong/weak positive/negative) can be identified

Question 13

Measures of spread of data

Answer 13

-Range
-IQR
-Standard deviation

Question 14

Standard deviation formula

Answer 14

Standard deviation= square root of (sum of (x- mean)^2)/n