According to a report from a business intelligence company, smartphone owners are using an average of 22 apps per month. Assume that number of apps used per month by smartphone owners is normally distributed and that the standard deviation is 7 If you select a random sample of 25 smartphone owners, what is the probability that the sample mean is between 21 and 22?

According to a report from a business intelligence company, smartphone owners are using an average of 22 apps per month. Assume that number of apps used per month by smartphone owners is normally distributed and that the standard deviation is 7 If you select a random sample of 25 smartphone owners, what is the probability that the sample mean is between 21 and 22?

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

Most graduate schools of business require applicants for admission to take the Graduate Management Admission Council's GMAT examination. Scores on the GMAT are roughly normally distributed with a mean of 527 and a standard deviation of 112. If a prestigious business school will only take those students who score in the top 5%, what score would you need to have to be accepted? You would need a score of or higher (round to the nearest whole number)
In a research study, conducted by the National Institute of Health, 25 individuals were sampled measuring their triglyceride levels. If the distribution of triglyceride levels for 25 to 55 year old females has a mean of 211 mg/dl and a standard deviation of 46 mg/dl, what is the probability that our sample mean will be above 240?
In 2021, the CDC estimated the mean height of U.S. women aged 20 years old and over was 63.5 inches with a standard deviation of 5.2 inches. (https://www.cdc.gov/nchs/fastats/body-measurements.htm) What is the expected mean for a sample of 150 women? What is the standard deviation of the mean for a sample of 150 women? What is the probability of 150 women having a sample mean below 60 inches? What is the probability of 150 women having a sample mean above 65 inches? What is the probability of 200 women having a sample mean below 60 inches? Notice the change in sample size. What is the probability of 200 women having a sample mean above 65 inches?
Imagine a scenario where 100 people complete a self-esteem measure. Assume the standard deviation of their true scores is 24.05 and the variance of the random errors associated with responses is 418.89. What is the reliablity of these scores?
An energy study found that household use of electricity had a mean of 682 and a standard deviation of 551 kilowatt-hours. Suppose the distribution of energy use was normal. Using a table, calculator, or software that can give normal probabilities, find the proportion of households with electricity use greater than 1000 kilowatt-hours.
According to a marketing website, adults in a certain country average 51 minutes per day on mobile devices this year. Assume that minutes per day on mobile devices follow the normal distribution and has a standard deviation of 7 minutes. What amount of time spent today on mobile devices by an adult represents the 80th percentile?
Linda, a researcher in a technology company, obtained a sample of 270 smartphone owners from California. She wanted to investigate whether Californians were quicker or slower to buy the latest version of a smartphone than the people in the rest of the United States. Linda found the average number of days that Californians waited to buy the latest version of a popular smartphone to be 4. Smartphone owners in the rest of the country typically wait 6 days, with a standard deviation of 21.
A survey reported that in a recent year, the mean serum cholesterol level in milligrams per deciliter for U.S. adults was 198 with a standard deviation of 43. A random sample of 110 adults was chosen. What is the probability that the mean cholesterol level is between 193 and 202?
Fran is training for her first marathon, and she wants to know if there is a significant difference between the mean number of miles run each week by group runners and individual runners who are training for marathons. She interviews 42 randomly selected people who train in groups and finds that they run a mean of 47.1 miles per week. Assume that the population standard deviation for group runners is known to be 4.4 miles per week. She also interviews a random sample of 47 people who train on their own and finds that they run a mean of 48.5 miles per week. Assume that the population standard deviation for people who run by themselves is 1.8 miles per week. Test the claim at the 0.01 level of significance. Let group runners training for marathons be Population 1 and let individual runners training for marathons be Population 2. Step 2 of 3 : Compute the value of the test statistic. Round your answer to two decimal places.
Many people consider their smart phone to be essential! Communication, news, Internet, entertainment, photos, and just keeping current are all conveniently possible with a smart phone. However, the battery better be charged or the phone is useless. Battery life of course depends on the frequency, duration, and type of use. One study involving heavy use of the phones showed the mean of the battery life to be 11.25 hours with a standard deviation of 3.3 hours. Then the battery needs to be recharged. Assume the battery life between charges is normally distributed. (a) Find the probability that with heavy use, the battery life exceeds 12 hours. (Round your answer to four decimal places.)(b) You are planning your recharging schedule so that the probability your phone will die is no more than 5%. After how many hours should you plan to recharge your phone? (Round your answer to the nearest tenth of an hour.) hours
Nintendo is doing a classic game competition for the anniversary of Super Mario Bros. The average runtime for a straight playthrough is 1 hour and 58 minutes (with a standard deviation of 6 minutes). Out of all of the players who compete in this competition (120 players), the fastest 10% will get a chance at a special reward. What would be the benchmark playthrough time for this competition?
Weekly rental sales per transaction at Enterpremium Inc., have a population mean of $325 with a population standard deviation of $60. This morning, the national manager, Ruebin Sanders, was going to check out his computer to see how many customers are trying to check out the Entrepremium Inc.’s vehicles at that moment. He logged in the computer and saw 36 customers nation-wide trying to rent out cars for a week. But he could not wait until all these customers complete their reservations. So he exercised his probability theory that he learned from his MBA class to figure out the probability of the average rental charge of these 36 customers exceeds $350 ahead of time. Compute the probability that the sample mean will exceed $350?