Samples of size n=9 are selected from a population with mean=80 with standard deviation=18. What is the expected value for the distribution of sample means?

A population has an average of 200 with a standard deviation of 25.  A random sample of 64 items is chosen.  What is the smallest interval that will contain 91.46% of the sample means?   Standard error (3 decimal places) =  Z =  Larger sample mean (1 decimal place) =  Smaller sample mean (1 decimal place) =

IQs measured on a certain scale are normally distributed with a mean of 90 and a variance of 400. whats the probability that a random person will have an IQ between 120 and 130.   the IQ of 51 people was taken, a sample mean of 90 and standard deviation of 64 was obtained. does this support that people tend to have IQs<100? use a 5% level of significance.

Scores for men on the verbal portion of the SAT-I test are normally distributed with a mean of 509 and a standard deviation of 112(a)  If 1 man is randomly selected, find the probability that his score is at least 570.(b)  If 19 men are randomly selected, find the probability that their mean score is at least 570.19 randomly selected men were given a review course before taking the SAT test. If their mean score is 570, is there a strong evidence to support the claim that the course is actually effective?(Enter YES or NO)

A population has a mean p= 160 and a standard deviation o=22. Find the mean and standard deviation of the sampling distribution of sample means with sample size n= 45. The mean is H- = |, and the standard deviation is o- = (Round to three decimal places as needed.)

Having more than 1000 students in a year, assume that I choose a simple random samples of 30 final exams in my engineering economics class and compute the class average. The results show that 5% of the grades are over 2.1 and 5% are under 1.9. Using this information, determine (i) the population mean and (ii) the population standard deviation of the final exam.    DO NOT USE EXCEL & PLEASE SHOW ALL CALCULATIONS AND STEPS.

The number of sick days used yearly by employees at a company had a distribution with a mean of 7 and a standard deviation of 2.  Find the probability that the mean number of sick days used by a random sample of 34 employees exceeded 6.5 days.