Exam 13: Determining the Size of a Sample

A graph of the relationship between accuracy and size of the sample shows that accuracy increases dramatically up until sample sizes near 500. Thereafter, it takes much larger increases in sample size to gain increases in accuracy.

When determining sample size, the conventional approach would NOT be:

Sample accuracy refers to how close a random sample's statistic is to another random sample statistic drawn on the same population. If the two samples result in the same, or nearly the same, data, then one has achieved sample accuracy.

Zoom-IT is a high-technology firm specializing in electronic consumer products. In particular, the company has worked on expansion systems for LCD and plasma screens. The company has developed a method for expanding the 2-inch screen on Apple iPod video display units to 8 inches by increasing the weight of the iPod by only 3 ounces. The "pop out" screen relies on Space Age plastics and an electronic expansion system that works similar to camera shutters. The only drawback is that the add-on device costs an additional $350, more than the cost of the iPod. Before going into production and marketing, Zoom-IT CEO, Jane Ellen Roberts, decides she wants some evidence that the device will sell. She commissions the marketing research department to conduct a survey and the critical question asks for likelihood to purchase the product on a 10-point scale. The researchers, attempting to determine the ideal sample size, realize there is no former study on this issue on which they could estimate the standard deviation in the population. They are considering the expense of a small pilot test, but researchers James Hughes and Bennet Alford make a recommendation to:

When using nonprobability samples instead of probability samples, different formulas must be applied to determine the appropriate sample size that precisely balances desired accuracy, variability in the population, and level of confidence.

The size of a probability sample depends on the client's desired accuracy (acceptable sample error)balanced against the cost of data collection for that sample size.

A finite multiplier is used when the population, relative to the sample size, is:

Variability is defined as the amount of dissimilarity or similarity in respondents' answers to a particular question.

Variability (standard deviation)of a population where a mean is being estimated may be estimated by dividing the range by 6.

Which of the following statements is most accurate regarding the relationship between sample size and the sample representativeness?

It is "true" to say that, in practice, you can estimate variability in the population by using one of three methods: (a)set pq to the most conservative amounts of 50 percent/50 percent, (b)estimate pq based upon prior research studies, or (c)conduct a pilot study.

A study is to be performed for a local restaurant, McGuire's, and Mr. McGuire wants to know the awareness of the restaurant name as well as satisfaction with food, service, and prices. Furthermore, being in the restaurant business for many years, Mr. McGuire is certain that he has very different clientele depending on which meal and whether they are there during the weekdays or weekends. Therefore, he wants to know answers to these issues by subgroups such as those who have eaten lunch meals, dinner meals, weekday patrons, and weekend patrons. Given these analysis goals, which sample size approach should be considered?

Which of the following is the theory that allows us to say that if we conducted a survey 1,000 times, and we were to plot the answers to our survey, the plot would appear as a normal curve?

Generally, a small population situation is one in which the sample exceeds 5 percent of the total population size.

Researchers should follow to the sample size formula closely when calculating sample size. No other consideration, such as the cost to the client, should be considered, as it will surely lower the accuracy of the study.

You are going to use a purposive sample, a nonprobability sample, to collect data from fast-food restaurant customers. Which of the following concepts would be applicable to determining sample size?

What three factors are needed to calculate sample size?

If we know the level of confidence (1.96 for 95 percent), variability estimates, and the size of a sample, there is a formula that allows us to determine:

If we are using the sample size formula to be used when estimating a mean and we are trying to determine s, we are trying to indicate:

Which of the following is true with regard to variability?