time - Is there any difference between "monthly average" and "average per month"?



I have trouble understanding if I should use "monthly average" or "average per month" when asking someone to calculate monthly average of a variable, e.g. heating expenses. Is there any difference, if this payment happens every month or quarterly, and I want to know average per month?



Answer



Average per month" or ("average monthly") and "monthly average" (or "monthly mean") have different meanings.


Rather than speak about the "Average per month" it would be clearer to use "average cost per month". It can be used and calculated as follows:



  • For payments that are made every month - add up all the money spent on electricity during 12 months then divide by 12 to get the average per month (http://www.ehow.com/how_6391683_calculate-average-monthly-return.html)

  • For payments that are made at intervals greater than monthly divide by the number of months in the interval (eg. for electricity bills that come every quarter, divide the amount paid last quarter by 3 to get the Average per month.)

  • For amounts that are calculated more frequently than each month where you want to know the average you spend per month (eg Perhaps your phone bill lists your charges for each day, then to find the average per month you would add up, say, the 365 daily charges for a calendar year than divide by 12 to find the average per month.)


Monthly average (or monthly mean) would be used for something that is recorded more frequently than once per month when you want to know the average value of that quantity during a month. (http://www.answers.com/Q/How_do_you_calculate_monthly_average_balance) For example:



  • If your phone bill lists your charges for each day you would find the monthly average of your daily phone charges by adding up the daily charges for the days of, say, July and then divide by 31 ( as there are 31 days in July)


Unfortunately "monthly average" is not always used correctly (http://stats.oecd.org/glossary/detail.asp?ID=3722) It is best to state explicitly what quantity is to be averaged, as in the above example ("monthly average of your daily phone charges") so that your meaning is clear.


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