How can the weighted mean be found?
- Multiply each value by its weighting (wx).
- Find the sum of the results (Σwx).
- Find the sum of the weightings (Σw).
- Divide to find the mean (Σwx / Σw).
What are index numbers used for?
To show how prices change over time.
How can index numbers be calculated?
- Select a price to compare all the others to. It is usually the price for the earliest year. This number becomes the base number and its year is called the base period.
- Give the base number an index number of 100.
- Divide each price by the base value.
- Multiply stage 3 by 100.
What does a weighted index number show?
How the cost of an object has changed by taking into account the different items used to make it. It is weighted mean applied to index numbers.
How can the weighted mean index be found?
By using the formula (Σwx / Σw).
What is the retail price index?
A weighted index number used to measure changes in the cost of living.
How is the All Groups Index calculated?
- Multiply the weighting by the index.
- Find Σwx.
- Use the weighted mean index formula.
How can the crude birth rate be found?
number of births / population x 1000
How can the crude death rate be found?
number of deaths / population x 1000
How can the crude birth and death rates be found from a grouped frequency graph?
- Find the total number of births or deaths.
- Find the total population.
- Find the crude rate.
How can the standardised birth or death rate be found in a grouped frequency table?
- Find the birth or death rate for each group this is now x.
- Find the weighted mean using the standard population as the weightings.
- Now use the weighted mean formula.
