The president of a university wants to use the mean of a ma to estimate the average amount of time it takes students to get from one class to the next, and he wants to be able to state with 99% confidence that the error is at best of 0.25 minutes. If it can be assumed from experience that the population standard deviation is 1.40 minutes, how large should the sample be taken?

The board of examiners that administers the real estate broker’s examination in a certain state found that the mean score on the test was 450 and the standard deviation was 50.  If the board wants to set the passing scores so that only the top 5% of all applicants pass, what should the passing score be?  Assume that the scores are normally distributed.

The president of a college wants to determine the mean number of units that college students take per semester. How large of a sample is required in order to be 99% sure that a sample mean will be off by no more than 1.25 units? An initial study suggested that the standard deviation is approximately 2.1 units.

Engineers must consider the breadths of male heads when designing helmets. The company researchers have determined that the population of potential clientele have head breadths that are normally distributed with a mean of 6.1-in and a standard deviation of 1.2-in. In what range would you expect to find the middle 98% of most head breadths? Between and If you were to draw samples of size 44 from this population, in what range would you expect to find the middle 98% of most averages for the breadths of male heads in the sample? Between and Enter your answers as numbers. Your answers should be accurate to 2 decimal places

The 95% confidence interval of the variance of a population is computed as (12.367,21.761). Interpret this confidence interval.

Engineers must consider the breadths of male heads when designing helmets. The company researchers have determined that the population of potential clientele have head breadths that are normally distributed with a mean of 5.8-in and a standard deviation of 0.8-in. In what range would you expect to find the middle 95% of most head breadths? Between and If you were to draw samples of size 42 from this population, in what range would you expect to find the middle 95% of most averages for the breadths of male heads in the sample? Between and Enter your answers as numbers. Your answers should be accurate to 2 decimal places.

Engineers must consider the breadths of male heads when designing helmets. The company researchers have determined that the population of potential clientele have head breadths that are normally distributed with a mean of 7.1-in and a standard deviation of 0.8-in. In what range would you expect to find the middle 50% of most head breadths? Between and If you were to draw samples of size 59 from this population, in what range would you expect to find the middle 50% of most averages for the breadths of male heads in the sample? Between and Enter your answers as numbers. Your answers should be accurate to 2 decimal places. Question Help: MMessage instructor DPost to forum Submit Question P Type here to search 12 esc 米 17 %24 & 7 3. 4. 6 8. W R T. Y %23 10

If we meet these conditions, the sampling distribution of the mean will have a normal shape and ... The mean of the sampling distribution will be u, (i.e., the same as the population mean) and the standard deviation of the sampling distribution will be (that's the population standard deviation divided by the square root of the sample size). In the AP Stats Guy video, he talks about the number of text messages his students send during class. Suppose the average number of text messages his students send during class is u = 30 text messages. If we take samples of say, n = 36 students at a time, we would expect the mean of the sampling distribution we create to be the same as the population mean, 30 text messages. If we can further say that standard deviation of the number of text messages is 12 text messages, by how much would we expect the sample means to vary? (hint, use the formula above) text messages

Executives at a car dealership want to estimate the average age of their customers before making a television commercial. They want to be 90% confident that the mean age is ±2 years of the sample mean. If the standard deviation from a previous study is 12 years, how large should the sample be? 98 ODD 239 4 139