Estimate how many 12 inch rulers will be about the same lenght as the object

Afurniture store is having a weekend sale and is offering a 20% discount on patio chairs and tables the sales tax on furniture is 6.25%

Amayoral candidate would like to know her residents’ views on a tax on sugar drinks before the mayoral debates. she asks one thousand registered voters from both parties. these voters are an example of a census population convenience sample simple random sample

Which situation is an example of an observational study?