Every once in a while, you are doing a survey to measure one thing and you wind up getting some extra bonus information. I like to think of this as the “loose change in the seat cushions” of the survey world. In the case of the survey on attitudes about balcony smoking smoking on Holland America Lines’ cruise ships, we got some loose change in terms of the average age of the survey participants.
Bear in mind that this calculation was based on the first wave of survey respondents and that it is not an exact representation of the total Holland America demographic. It simply calculates the average age of the survey participants +/- 2.5 years. The demographic data was self reported, but we were only asking for an age range, not a specific age. The age range question method tends to get reasonably accurate responses. (An explanation of the methodology appears after the table.)
The average survey participant is about 58 1/2 years old.
|21 – 30||25.5||1%||0.255|
|31 – 40||35.5||3%||1.065|
|41 – 50||45.5||12%||5.340|
|51 – 60||55.5||34%||18.870|
|61 – 70||65.5||41%||26.855|
|71 – 80||75.5||8%||6.040|
|81 – 90||85.5||0%||0.000|
Methodology: For each age range, we can make the assumption that the average person in the range is at the midpoint, or average age for the range. For example, for the 51 – 60 age group, you would take all 10 of the possible ages in the group and add them together.
(51 + 52 + 53 + 54 + 55 +56 + 57 + 58 +59 + 60) = 555
Divide that total (555) by the number of choices (10) and you get a midpoint/average age for the range of 555/10 = 55.5. It works the same for each range. These are the values you see in the 2nd column of the table.
The third column shows the percentage of respondents who were in that range. (This data comes from the Intermediate Readout Report for the Balcony Smoking survey here.) If we multiply the Average Age (Column 2) by the Percentage of respondents in that age bracket (Column 3), we get the number of years that particular bracket contributes to the total (Column 4.)
Add up the numbers in Column 4 and you get the Average Age of the participant. I stated the number as being within 2.5 years in either direction to account for potential error.