The United States Postal Service reports that 90% of first-class mail within the same city is delivered in two days of the time of mailing. Ten letters are randomly sent to different locations. What is the mean number of letters that will arrive within two days? What is the standard deviation of the number of letters that will arrive within two days?

The United States Postal Service reports that 90% of first-class mail within the same city is delivered in two days of the time of mailing. Ten letters are randomly sent to different locations. What is the mean number of letters that will arrive within two days? What is the standard deviation of the number of letters that will arrive within two days?

A First Course in Probability (10th Edition)

10th Edition

ISBN:9780134753119

Author:Sheldon Ross

Publisher:Sheldon Ross

Chapter1: Combinatorial Analysis

Section: Chapter Questions

Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...

See similar textbooks

Similar questions

The tallest living man at one time had a height of 220 cm. The shortest living man at that time had a height of 136.8 cm. Heights of men at that time had a mean of 173.88 cm and a standard deviation of 5.13 cm. Which of these men had the height that was more extreme?
Of the 200 American film enthusiasts, the average age is: 30 years, while the standard deviation is 5 (five) years. Question What is the age limit for American film fans who are classified in the 12% of the film fans group?
The U.S. Center for Disease Control reports that the mean life expectancy was 47.6 years for whites born in 1900 and 33.0 years for nonwhites. Suppose that you randomly survey death records for people born in 1900 in a certain county. Of the 124 whites, the mean life span was 45.3 years with a standard deviation of 12.7 years. Of the 82 nonwhites, the mean life span was 34.1 years with a standard deviation of 15.6 years. Conduct a hypothesis test at the 0.05 level of significance to see if the mean life spans in the county were the same for whites and nonwhites. a) The null and alternative hypothesis would be: O Ho: Pw = PN H1: Pw > PN Mil :ºH H1: Hw + HN %3D O Ho: Pw H1: Pw µN Ho: µw H1: µw 0.05 d) Make a decision. O Fail to reject the null hypothesis O Reject the null hypothesis
A group of customer service surveys were sent out at random. The scores were 40, 70,80, 00, 50, 40, 40, 70, 80, 00, and 50. Find the range, variance, and standard deviation
In a survey, 80% of the voters support a particular referendum. If 30 voters are chosen, find the standard deviation of the number of voters who support the referendum.
A study by the National Center for Health Statistics suggested that women between the ages 20 and 29 in the US have a mean BMI of 26.8 with a standard deviation of 7.4. A BMI of 30 or greater is considered as being obese. What proportion of women in this age range are obese?
4 student obtained the mean and standard deviation of 100 observations as 40 and 5 respectively. It was later discovered that he had wrongly copied down an observation as 50 instead of 40. Calculate the correct mean and standard deviation.
A banker finds that the number of times people use automated-teller machines (ATMs) in a year are normally distributed with a mean of 40.0 and a standard deviation of 11.2 (based on data from Maritz Marketing Research, Inc.). Find the proportion of customers who use ATMs between 20 and 60 times. Use four decimal places for your answer
The average wage for bank managers in a certain city is $91,900 per hour with a standard deviation of $24,300. What should be the hourly wage for an administrator if he/she wishes to earn less than 25% of all employees?
Most medical schools require applicants for admission to take the Medical College Admissions Test (MCAT) examination. Scores on the MCAT are roughly normally distributed with a mean of 500 and a standard deviation of 10.6. What percentage of students score above 518 points? ( write as a decimal and round to the nearest hundredth)
According to a website, the mean number of apps on a smartphone in the United States is 85. Assume the number of apps is normally distributed with mean 85 and standard deviation 23. What proportion of phones have fewer than 99 apps? Round the answer to four decimal places. The proportion of phones that have fewer than 99 apps is .
2. 60 matches were played in a football tournament. The table to the right shows the number of goals scored in all matches. Number of Goals 1 3 4 5 Number of Matches 18 20 3 a. Find the median number of goals scored per match. b. Find the mean number of goals scored per match. c. Calculate the standard deviation of the goals scored per match.