Imagine a toilet in a home with two healthy adults (a male and a female), and two healthy children (say, nine and six years old). Out of x number of visits to that toilet over a period of time, how many will be just a #1 and how many will be a #2 (or a #1 and a #2)?
Or to put this in other words, the average urination:defecation ratio for a human is _____?
I’ve read the average is between 1 bowel movement every 2-3 days up to 2-3 bowel movements a day. Personally I couldn’t imagine only shitting once every couple days though, that seems odd.
The average will be off if you don’t count #3, #4, #5, and #6 also.
It varies greatly depending on your diet and exercise regime etc. I think for most people once a day or once every two days is typical, but 2 or 3 times a day may be normal for a particular individual.
To actually answer the OP’s question, I’m gonna WAG it at 5:1 for men and 8:1 for women. I don’t think kids vs. adults would matter.
My personal experience is my cite. I leave the serious research to others.
Figure on about 7 number ones for every number 2 unless you’re in India.
One study found that healthy men urinate a median of 6 times during the day and 0.5 times at night. Cite: Age and volume dependent normal frequency volume charts for healthy males - PubMed
Another study found that healthy men urinate a median of 7 times per 24 hours. Cite: Voiding frequency in a sample of asymptomatic American men - PubMed
Healthy women urinate a median of 7 or 8 times per 24 hours. Cite: Variability of 24-hour voiding diary variables among asymptomatic women - PubMed
British men and women in answering a questionnaire claimed a median bowel movement frequency of 7 times per week or once a day. The same participants were asked to keep a journal of their bowel movements. The journal data were found to confirm that median frequency is indeed just about once per day. Cite: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1379343/pdf/gut00573-0122.pdf
A study in Eastern India of men and women found median bowel movement frequency of 14 per week or twice per day. Cite: Defecation frequency and stool form in a coastal eastern Indian population - PubMed
One bowel movement per day is average in Italian adults. Cite: http://www.researchgate.net/profile/Filippo_Pucciani/publication/8681744_An_extended_assessment_of_bowel_habits_in_a_general_population/links/0fcfd510134bea37b3000000.pdf
One bowel movement per day is the median in preschool age children. Cite http://adc.bmj.com/content/59/7/649.full.pdf
This may tie in with the design of modern low-water-usage toilets. Many people have complained about low-flush toilets not doing a complete water change, and often needing two flushes after a #2. (This was more so in the earlier days of low-flush toilets. Design have apparently improved more recently.)
Dave Berry did an article on low-flush toilets some years back, which raised such a massive popular response that he did at least two follow-up articles on it.
Cecil Himself discussed the question here. TL;DR: People pee a lot more often than they poop. So, a toilet designed to need just one flush after a pee but two flushes after a poop may be the optimal design for water conservation.
Living in the country now, “P” & “Poop” together is my ratio for the toilet. So, a one to one ratio.
I do “P” more than that but I waste no water with the toilet doing it. 
What day of the week is it and do both parents work