- A researcher wants to estimate the percentage of all adults that have used the Internet to seek pre-purchase information in the past 30 days, with a tolerable sampling error (E) of 0.03 and a confidence level of 97.5%. If secondary data indicated that 25% of all adults had used the Internet for such a purpose, what is the sample size? See page 312 of your text book.
Level of Significance = 0.025
z Score of ½ of Level of Significance = 2.24
Sampling Error, E = 0.03
σ = 0.75
n = ( z2 * σ2 ) / E2
n = 1046.64 = 1047
Sample size = 1047
- A researcher wants to estimate a population mean. The level of tolerable sampling error is 0.2 of a purchase occasion, with a confidence level of 95.44%. If the estimated population variance is 5 for the most important question in the study, what is the desired sample size? See page 310 of your text book.
From the z table, z score for 95.44% is 1.69.
n = ( z2 * σ2 ) / E2 = (1.692 x 52 ) / 0.22 = 1785
1) at 95.44% confidence, Z = 2
2) sample means formula is appropriate
3) Variance = 5
4) Tolerable Error = .2
5) Computed Sample size of 500.