Here are some numbers that you can use to sharpen your computational skills for sample size determination. Crest Toothpaste is reviewing plans for its annual survey of toothpaste purchasers. With each case that follows, calculate the sample size pertaining to the key variable under consideration. Where information is missing, provide reasonable assumptions.

Variability 23% share last year Unknown 30% switched last Kev Variable Acceptable Error +) 490 Confidence Level Market share of Crest Toothpaste Percent ofpeople who brush their teeth per week 95% 5% 00% How likely Crest buyers are to switch brands 5% 95% ear Percent ofpeople who want tartar-control features in their toothpaste Willingness ofpeople to adopt the toothpaste brand recommended by their family dentist 20% two years ago: 40% one year ago 3.5% 95% Unknowm 6% 00%