In order to help answer your question you need to define what you deem to be an average person. I expect in your case you are talking of a professional retail trader who trades full time?
Before I give you a few scenarios you need to realise that there are many factors that impact on how many trades are taken and none more so than the strategy itself. The examples below will give you an idea of what a typical day may look like and how many trades are taken.
Day Trader working 0800-1600- Using 15 min chart for entries
Can take multiple trades throughout the day usually during times of higher volatility eg. London and New York Open. The trader might be looking at several currencies as well as equities and commodities. For this reason they may have several trades all at once.
Day Trader working 0800-1600 - Scalper looking at 5 min Chart
Shorter term trader who often does not hold onto trades for long and needs to have laser like focus. For this reason they will often analyse several instruments but only trade one at a time. They will open and close several trades throughout the day.
The trader will often analyse the markets as a whole looking at longer terms trends, correlations and fundamentals. Many swing traders will trade Forex, equities and commodities all at the same time. The trader will have a few positions open at anyone time but the amount of trades taken is far less.
I must reiterate the above examples are just a generalisation and will vary on many more factors.
Now for yourself moving forward, you must first decide on the type of trading you will be doing. I assume you do not have a trade plan as yet so creating one should be your first priority.
I personally would recommend as you are beginner to trade only one position at a time. If you do want to day trade start with a higher time frame and work down not the other way around. You will find a time frame that you are both comfortable trading with and that suits your personality.
But remember, follow your plan. Let the market come to you, never go chasing trades! If trades present themselves according to your plan, take them! If they don't sit on the sidelines and wait!
It is better to be out of the market wishing you were in, than in the market wishing you were out!!!