"once a day" vs. "once every day"

Question

I am building a survey and asking the participants:

How often do you think about your online security?

The answers are:

1. At least once every day
2. At least once every week (and less than once every day)
3. At least once every month (and less than every week)
4. At least once every 6 months (and less than every month)
5. Once a year
6. I do not think about it at all
7. Other (specify)

My questions are:

1. Is "once a day" equivalent to "once every day"?
2. Is the clarifications between circle brackets necessary? For example, in

At least once every week (and less than once every day)

The reason for me to add the sentence in the circle brackets is because since I mention "at least" once every week, this mean one or more times every week, which can be equal to once or more every day (so I want to be precise it is less than once every day). Does this make sense? Or otherwise, it can be removed? Because if the word "at least once every week" means the thing (the thinking in our question) occurs per week, then I think the between brackets clarification is not correct. Because the occurrence is not distributed among the week days, but happens once or more at one day every week?

EDIT: Also, do you see anything vague or incorrect in modifying the scale to:

• Every day
• Every week
• Every month
• Every 6 months
• Once a year
• I do not think about it at all
• Other (specify)

Because it was like this before, but someone asked me, how many times a week?

Answer 1

"Once a day" and "every" can sometimes be interchangeable. It all depends on context. There are times when using both together might add some needed clarification, but other times when it is unnecessary.

For example, if your Doctor gave you 14 days' worth of medication and told you to take it "once a day", it ought to be obvious that he means once every day until the course of 14 days has run. There is no need to add "every". On the other hand, if someone said "I have to take this medication every day" that could mean they have to take it for the rest of their life.

Similarly, if someone said "I work every day", that might not mean literally every day of the week, year after year without a break. It might just mean every usual work day - such as Monday to Friday - and they just mean to distinguish themselves from a part-time worker who only works some of the usual 'full-time' working week.

In your example, "online security" could be someone's line of work. They may think about it every work day, but not every day without exception. Personally, I don't think the option has been written this way so as to exclusively mean 7 days a week as opposed to 5, but I think it may have been written that way to avoid all of the ambiguity I have just discussed. Interpret it how you want.

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Just on a general note, I've seen your various posts picking apart these kinds of multiple-choice survey options. To be honest, you may be seriously over-thinking them. The options don't always make sense to us as native speakers anyway. For example, terms like "strongly agree" and "strongly disagree" are often used alongside "agree" and "disagree", which doesn't stand up to scrutiny. One either agrees wholly, or does not. Survey writers tend to settle on a scale for the answers and then apply that scale to a set of questions for consistency, but without any thought for grammar.

Answer 2

Both "once a day" and "once every day" are fine (as is "once per day") but once a day sounds more natural.

"Once every day" has the emphasis on it being extremely important that you don't miss a day. Such as a doctor telling you to take your medicine once every day. This doesn't really apply here.

"Once per day" is similar to "once a day" but a bit more formal. Probably more formal than is necessary here but it wouldn't be weird. I would choose whichever you like between "Once a day" and "once per day".

On most selections like this, the clarification you have provided in the brackets is omitted. It is implied that you select the most frequent one that applies. I would have no problem interpreting the question and answering correctly without the extra information in brackets but I don't have any information about comparing the accuracy of results obtained between the two.

To me, there is too much information when you include the brackets. People like to complete surveys with as little reading as possible. If you really want to make it clear I would specify something like "Please select only the most frequent option that applies" in the question.

I personally see nothing wrong with modifying the scale to "Every day" etc. I think this is quite a common phrasing for surveys. However, if you are receiving negative feedback about it from survey participants then it is probably worth avoiding.

Sidenote: "(specify)" should probably be "(Please specify)". This is much more common as it sounds less demanding.