EX: The 2017-2018 APPA National Pet Owners Survey
https://americanpetproducts.org/Uploads/MemServices/GPE2017_...
Overall dog ownership in the US at 48% +/- 4.4 based on 505 completed surveys. But, that's not nearly enough data to slice things down to 30-40 year olds and worse it's a servery which have dubious accuracy overall.
Their methodology as outlined on their web site (https://store.mintel.com/mintel-methodology) and details the quotas they utilize to get what they feel is a statistically relevant cross section of data.
Anytime sampling is used, of course it's not going to be exact. But a 2000 person survey is, given equal statistical rigor, going to be better than a 500 person online survey and might be enough of a population to justify more detail.
(Unfortunately, the Mintel survey results cost $4300, so other than their methodology page it's going to be difficult for me to infer much more. But the methodology page seems to suggest they aim for +/-2 or 3% confidence level.)
Now, if they had sampled ~20,000 people then sure you can slice and dice like that. But slicing data always increases the risk of sampling bias as would anything that targets 30-39 year olds specifically.
