27. On a standardized test with a normal distribution, the mean was 64.3 and the standard...
Scores on a standardized test are normally distributed with a mean of 100 and a standard deviation of 20. If these scores are converted to standard normal Z scores, which of the following statements will be correct?
The batteries from a certain manufacturer have a mean lifetime of 850 hours, with a standard deviation of 90 hours. Assuming that the lifetimes are normally distributed, complete the following statements. (a) Approximately _______ of the batteries have lifetimes between 760 hours and 940 hours.(b) Approximately 95% of the batteries have lifetimes between _______ hours and _______ hours.
3. According to data, the mean quantitative score on a standardized test for female college-bound high school seniors was 500. The scores are approximately normally distributed with a population standard deviation of 100. What percentage of the female college-bound high school seniors had scores above 725? Use a standard normal table or appropriate technology.
Problem 4. The lifetime of a certain battery follows a normal distribution with a mean of 276 and standard deviation of 20 minutes. (a) What proportion of the batteries have a lifetime more than 270 minutes? (b) Find the 90th percentile of the lifetime of these batteries. (c) We took a random sample of 100 batteries. What is the probability that the sample mean of lifetimes will be less than 270 minutes?
Given a standardized normal distribution (with a mean of 0 and a standard deviation of 1) complete parts (a) through (d) below. Click here to view page 1 of the cumulative standardized normal distribution table, Click here to view page 2 of the cumulative standardized normal distribution table. a. What is the probability that Z is between 1.57 and 1.83? - The probability that Z is between 1.57 and 1.83 is (Round to four decimal places as needed.) particular train...
According to the data, the mean quantitative score on a standardized test for female college-bound high school seniors was 500. The scores are approximately Normally distributed with a population standard deviation of 100. What percentage of the female college-bound high school seniors had scores above 637? Answer this question by completing parts (a) through (g) below. e. Use the Normal table to find the area to the left of the z-score that was obtained from a standardized test score of...
A particular IQ test is standardized to a Normal model, with a mean of 80 and a standard deviation of 12. Using the Empirical rule determine about what percent of people should have IQ scores less than 44? The percent of people with IQ scores less than 44 is:
BIG Corporation produces just about everything but is currently interested in the lifetimes of its batteries, hoping to obtain its share of a market boosted by the popularity of portable CD and MP3 players. To investigate its new line of Ultra batteries, BIG randomly selects 1000 Ultra batteries and finds that they have a mean lifetime of 946 hours, with a standard deviation of 84 hours. Suppose that this mean and standard deviation apply to the population of all Ultra...
A particular IQ test is standardized to a Normal model, with a mean of 90 and a standard deviation of 9. Using the Empirical Rule determine about what percent of people should have IQ scores more than 108? The percent of people with IQ scores more than 108 is: Number % (Omit the percent sign)
David scored 942 on a standardized achievement test. The mean test score was 850 with a standard deviation of 100. Assuming that the distribution of test scores was normal,and using Table 8.1, what percent of students scored higher than David?