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Mustel Group explains how ‘statistically valid survey’ measured public support for North Cowichan forests

Evi Mustel provides a simple analogy for the seemingly complex field of statistically valid surveys.

“You can make a pot of soup, but you don’t need to eat the whole pot to know what it tastes like,” says the principal of Vancouver-based market-research firm, Mustel Group. “Just a teaspoon, a small bowl, a sampling of it, and you get a sense.”

That’s what sampling is all about, Mustel says, making sure you obtain a representative sample of the whole — a community’s demographic profile, including age and gender.

“It’s quality, not quantity,” she says of the results.

The Mustel Group conducted a statistically valid survey of 215 North Cowichan residents for the second phase of public consultation on the future of the Municipal Forest Reserve.

The firm randomly sought out residents who were 18 years and older, phoning homes in the evenings during the week and during the day on weekends — but not in the day during the week when older women tended to be over-represented.

Statistics Canada reported that North Cowichan had a population of 31,990 in 2021. Closer to 26,000 of those residents were 18 years or older.


The phone numbers were drawn randomly from a regularly up-dated database of published residential listings, including both landlines and cell numbers in the community.

Residents were each provided a unique link that allowed them to review and consider background information and options before completing the on-line survey, choosing from four potential management scenarios for the forest reserve.

The margin of error on the sample is conservatively estimated at plus-or-minus 6.7 per cent 95 per cent of the time. “It’s all based on Statistics 101,” Mustel said. “If we repeated the survey…95 out of 100 times the results would fall within that range. It’s a standard calculation used in market research….”

If Mustel had reached out to 500 people instead of 215, the margin of error would have dropped to plus-or-minus 4.4 per cent — but at a greater financial cost to the municipality.

The results showed that 38-per-cent of the 215 individuals named Active Conservation as their preferred choice.

That’s down only slightly from 41-per-cent support among 1,922 individuals— 63 per cent of them from North Cowichan — who filled out the same survey on an open-access basis.

When the two conservation options — Active and Passive – are added together, open — on-line showed 76-per-cent support compared with 67 per cent in the statistically valid survey.

“The open-access tended to attract people with strong opinions, one way or the other,” Mustel said. “They were much more engaged in the process.

“But we’re fortunate that the results do support both, they’re not dramatically different. They certainly indicate the same leaning.”

The two logging scenarios — Status Quo and Reduced Harvest — lagged far behind in public support.

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— Larry Pynn, March 13, 2023

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