SUMMARISING DATA and CORRELATION

Question 1

What is an average?

Answer 1

An average is a single value used to describe a set of data as a measure of central tendency.

Question 2

What are the 3 type of averages?

Answer 2

Mode, Median and Mean.
* The mode is the value appearing most often.
* The median is the middle value when all the values are in order.
* To work out the mean, add up all the values and divide by the number values.

Question 3

What is meant by transforming data?

Answer 3

When all data values are transformed (increased or decreased) by the same amount or percentage, the averages are transformed by the same amount or percentage.

Question 4

What are the two ways to measure dispersion or spread?

Answer 4

Range and Interquartile range.

Question 5

Whats the formula to calculate the range of a data set?

Answer 5

Range = largest value - smallest value

Question 6

Whats the formula to calculate the interquartile range of a data set?

Answer 6

Interquartile range = (IQR) = (Q3) - lower quartile (Q1)

Question 7

What is Box plot used to display?

Answer 7

Box plots are used to display the minimum value,
the maximum value, the lower quartile, the upper
quartile and the median from a distribution.

Question 8

What are the advantages of Mode?

Answer 8

• Easy to find and always a data value
• Can be used with any type of data
• Unaffected by open-ended or extreme values

Question 9

What are the disadvantages of Mode?

Answer 9

• May not exist
• Cannot be used to calculate
  a measure of spread

Question 10

What are the advantages of Median?

Answer 10

• Unaffected by extreme values
• Can be used to help calculate quartiles,
  interquartile range and skew

Question 11

What are the disadvantages of Median?

Answer 11

• May not be a data value

Question 12

What are the advantages of Mean?

Answer 12

• Uses all the data
• Can be used to calculate standard deviation
  and skew

Question 13

What are the disadvantages of Mean?

Answer 13

• Always affected by open-ended or extreme values
• Rarely a data value

Question 14

What are the golden rules when comparing data?

Answer 14

• always work out an average and make a comment
• always work out a measure of spread and make a comment.

Question 15

What are the two types of variables?

Answer 15

The explanatory (independent) variable
(the one you change) is plotted on the horizontal (x ) axis.

The response (dependent) variable (the one that
responds to, or depends on, the (explanatory variable) is plotted on the vertical (y ) axis.

Question 16

What is scatter diagram used for?

Answer 16

Scatter diagrams are used to show whether two sets of data are associated. This means there is a relationship between them.

Question 17

Define correlation

Answer 17

Correlation describes the association, which can show an increasing or decreasing trend. Correlation
can be strong or weak.

Question 18

Define causal relationship

Answer 18

A causal relationship between two variables means that a change in one of the variables directly causes a change in the other variable, such as the number of hours of sunshine and
the temperature, or the age of a car and its value.

Question 19

What does Spearman’s rank correlation coefficient measures?

Answer 19

Spearman’s rank correlation coefficient, measures the strength of the correlation
between two sets of data.

The value for Spearman’s rank correlation coeffi cient lies between -1 and +1. The further the value is from zero, the stronger the correlation.