What is an average?
An average is a single value used to describe a set of data as a measure of central tendency.
What are the 3 type of averages?
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.
What is meant by transforming data?
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.
What are the two ways to measure dispersion or spread?
Range and Interquartile range.
Whats the formula to calculate the range of a data set?
Range = largest value - smallest value
Whats the formula to calculate the interquartile range of a data set?
Interquartile range = (IQR) = (Q3) - lower quartile (Q1)
What is Box plot used to display?
Box plots are used to display the minimum value,
the maximum value, the lower quartile, the upper
quartile and the median from a distribution.
What are the advantages of Mode?
- Easy to find and always a data value
- Can be used with any type of data
- Unaffected by open-ended or extreme values
What are the disadvantages of Mode?
- May not exist
- Cannot be used to calculate
a measure of spread
What are the advantages of Median?
- Unaffected by extreme values
- Can be used to help calculate quartiles,
interquartile range and skew
What are the disadvantages of Median?
- May not be a data value
What are the advantages of Mean?
- Uses all the data
- Can be used to calculate standard deviation
and skew
What are the disadvantages of Mean?
- Always affected by open-ended or extreme values
- Rarely a data value
What are the golden rules when comparing data?
- always work out an average and make a comment
- always work out a measure of spread and make a comment.
What are the two types of variables?
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.
What is scatter diagram used for?
Scatter diagrams are used to show whether two sets of data are associated. This means there is a relationship between them.
Define correlation
Correlation describes the association, which can show an increasing or decreasing trend. Correlation
can be strong or weak.
Define causal relationship
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.
What does Spearman’s rank correlation coefficient measures?
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.
