What is standard deviation used for?
To measure spread. It looks at how far away the individual numbers are from the mean.
How can the standard deviation be found for frequency tables?
- Find fx for all the x values.
- Find fx^2 for all the x values.
- In the standard deviation formula, put an f before all the x’s and replace n with Σf.
How can the standard deviation be found for grouped frequency tables?
- X is the midpoint.
2. Follow the same method as for frequency tables.
What happens to the mean if all the values change by the same amount?
The mean increases by said amount.
What happens to the standard deviation of all the values change by the same amount?
The standard deviation stays the same.
What happens to the mean if all the values are multiplied or divided by the same amount?
The mean is multiplied by said amount.
What happens to the standard deviation if all the values are multiplied or divided by the same amount?
The standard deviation is multiplied by said amount.
How can variance be calculated?
By squaring the standard deviation.
