For a random sample of n=16 selected from a normal distribution with a mean of µ =75 and a σ = 20, Find the range of sample means that defines the middle 95% of the distribution of sample means. In you answer be sure to include the standard error, z-score and range.

Discribe the scores in a sample that has a standard deviation of zero.

A large number of applicants for admission to graduate study in business are given an aptitude test. Scores are normally distributed with a mean of 460 and standard deviation of 80. What fraction of the applicants would you expect to have a score of 350 or above?

A standardized​ exam's scores are normally distributed. In a recent​ year, the mean test score was 1471 and the standard deviation was 317. The test scores of four students selected at random are 1900​,1200​,2200​,and 1370. Find the​ z-scores that correspond to each value and determine whether any of the values are unusual.

2000 freshmen at state university took a biology test. the scores were normally distributed with a mean of 70 and a standard deviation of 5. Use z scores. (1) the percent of students that scored less than 77

Deanna is the principal at a Midwestern middle school and wants to know the average IQ of all female, seventh grade students.  She does not know anything about what the population distribution looks like.  She took a simple random sample of 31 seventh-grade girls in her school and found the average IQ score in her sample was 105.8 and the standard deviation was 15. Using the sample standard deviation above to estimate the population standard deviation, what is the minimum sample size needed for a 99.5% confidence interval to have a margin of error of no more than 2.3?

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