Tuesday

April 28, 2015

April 28, 2015

Number of results: 22,250

**Statistics**

Suppose that a sample of 50 scores has a mean of Y=90 and the standard deviation is 15. Between what two values of Y will at least 90% of the scores fall? What is the maximun number of scores that can lie out of the interval?
*October 30, 2011 by Sara*

**Statistics**

The lifetimes of batteries produced by a firm are known to be normally distributed with a mean of 100 hours and a standard deviation of 10 hours. What is the probability a battery will last between 110 and 120 hours?
*November 24, 2011 by Brea*

**statistics**

The lifetime of a 2 volt non-rechargeable battery has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours. What is the z- score for batteries with lifetimes of 520 hours
*September 3, 2012 by Gee*

**statistics**

The lifetime of a 2 volt non- rechargeable battery has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours.What is the z- score for batteries with lifetimes of 600 hours
*September 3, 2012 by Gee*

**statistics**

Waiting times at a doctor office are normally distributed with a mean of 35 minutes, and a standard deviation of 10 minutes. What is the chance a patient would have to wait over 50 minutes?
*November 5, 2014 by Cecy*

**Psychology**

Twenty students randomly assigned to an experimental group receive an instructional program; 30 in a control group do not. After 6 months, both groups are tested on their knowledge. The experimental group has a mean of 38 on the test (with an estimated population standard ...
*September 19, 2011 by summer*

**statistics**

A coin mint has a specification that a particular coin has a mean weight of 2.5 g. A sample of 39 coins was collected. Those coins have a mean weight of 2.49491 g and a standard deviation of 0.01372 g. Use a 0.05 significance level to test the claim that this sample is from a ...
*March 7, 2015 by slomomo*

**statistics**

A cell phone service provider has selected a random sample of 20 of its customers in an effort to estimate the mean number of minutes used per day. The results of the sample included a sample mean of 34.5 minutes and a sample standard deviation equal to 11.5 minutes. Based on ...
*February 22, 2015 by timothy kendricks*

**Pyschological Statistics**

In a distribution with a standard deviation of eight, an individual score of 42 corresponds to a Z score of -0.5. What is the mean of this distribution?
*October 8, 2014 by Monique*

**statistics**

A charity believes that when it puts out an appeal for charitable donations the donations it receives will normally distributed with a mean of $50 and standard deviation of $6, and it is assumed that donations will be independent of each other. (i) Find the probability that a ...
*February 15, 2011 by Probability*

**Statistics**

Find the margin of error for a 95% confidence interval for estimating the population mean when the sample standard deviation equals 100, with a sample size of (i) 400, (ii) 1600. What is the effect of the sample size? (b) Find the margin of error for estimating the population ...
*April 5, 2015 by courtney*

**statistics**

Boxes of bran flakes are known to be normally distributed with a mean weight of 475g and a standard deviation of 10g.Calculate the probability of a box having a weight exceeding 485 grams. Calculate the probability that the mean weight of sixteen boxes will exceed 480g.
*March 2, 2013 by Sue*

**statistics**

the weights of shells follow a normal distribution. a random sample of 12 hybrid shells a a mean weight of 1.7 pounds with standard deviation 0.24 pounds. Find a 95 % confidence interval level for the mean weight if the fall catch is within 0.1 pounds of the sample estimate
*March 21, 2013 by Lost37*

**Statistics**

A local grocery store wants to estimate the mean daily number of gallons of milk sold to customers. Assume the number of gallons sold follows the normal distribution, with a population standard deviation of 5.10 gallons. A random sample of 60 days shows that the mean daily ...
*October 27, 2013 by Joey*

**college statistics**

a set of data is normally distributed with a mean of 1000 and a standard deviation of 100.what would be standard score for a score of 900.what percent of scores is betyween 1000 and 900.what would be percentile rank for a score of 900.
*June 3, 2012 by melba*

**statistics-normal distribution**

a set of data is normally distributed with a mean of 500 and a standard deviation of 100. a) what would the standard score fora score of 700 be? b) what % of scores is between 500 and 700? c) what would the percentile rank for a score of 700?
*October 28, 2010 by mary- can someone please solve,lost*

**statistics**

set of data is normally distributed with a mean of 200 and standard deviation of 50. · What would be the standard score for a score of 300? · What percentage of scores is between 200 and 300? · What would be the percentile rank for a score of 300? (Points : 6)
*August 26, 2011 by Laynette*

**statistics**

The MacBurger restaurant chain claims that the waiting time of customers for service is normally distributed, with a mean of 3 minutes and a standard deviation of 1 minute. The quality-assurance department found in a sample of 50 customers at the Warren Road MacBurger that the...
*June 23, 2008 by Renee*

******HELP**** STATISTIC**

The table below shows the probability distribution of the types of food purchased by students from the school cafeteria. What is the probability a student has purchased Caesar salad? (2 points) 0.17 Suppose houses are available for purchase during construction of a new ...
*March 25, 2014 by Tikima*

**statistics**

The following information is available. H0: μ ≤ 10 H1: μ> 10 The sample mean is 12 for a sample of 36. The population standard deviation is 3. Use the .02 significance level.
*July 21, 2011 by Anonymous*

**statistics**

In a normal distribution with the mean being 500 and the standard deviation being 100, what raw score separates the top 40% of a distribution from the rest?
*July 29, 2012 by Jessica *

**statistics**

In a normal distribution with the mean being 500 and the standard deviation being 100, what raw score separates the top 40% of a distribution from the rest?
*July 29, 2012 by Jessica *

**statistics**

A normal distribution has a standard deviation equal to 23. What is the mean of this normal distribution if the probability of scoring above x = 181? record to 1 decimal place
*June 21, 2013 by Paisley*

**Statistics**

A random sample of 47 students studied for an average of 7.1 hours last week. If the population standard deviation is 1.2 hours, what is the 90% confidence interval for the population mean?
*April 18, 2014 by Monica*

**statistics**

Let x be a continuous random variable that is normally distributed with a mean of 24 and a standard deviation of 7. Find the probability that x assumes a value between 27.5 and 59.0. Use Table IV in Appendix C to compute the probabilities. Round your answer to four decimal ...
*April 18, 2011 by Katie*

**statistics**

An automotive manufacturer has selected 10 car seats to study the Rockwell hardness of the seat recliner mechanism. A sample of 8 has an average of 44.795 and a standard deviation of 0.402. At 95% percent confidence level, what is the interval for the population mean?
*February 9, 2015 by t*

**Probability of Mean (Statistics)**

Assume 20 oz. cola bottles are filled so that the mean amount of liquid contained in the bottle is 20 oz and the standard deviation is .12 oz. If a case of 24 bottles is randomly selected from the population of all soda bottles, find the probability that the mean number of ...
*June 22, 2008 by thomas*

**statistics**

Someone who has never seen a normal die before decides to estimate the mean value of all its faces (μ) by rolling it many times. First, they are told that the standard deviation is σ = 1.7. Then, they roll the die 50 times and get a sample mean of x-bar = 3.7. ...
*January 29, 2012 by Nadia*

**statistics**

historically, the average customer spends $8.53 for all TGP restaurants(u=8.53). If the population standard deviation is $1.06(o=1.06) and the data is normally distributed, find the probabiltiy that the sample mean will be within $.15 of the populaiton mean using a sample size...
*February 27, 2015 by angela*

**Help Please Statistic**

7. The table below shows the probability distribution of the types of food purchased by students from the school cafeteria. What is the probability a student has purchased Caesar salad? (2 points) 0.17 Suppose houses are available for purchase during construction of a new ...
*March 24, 2014 by Tikima*

**Math**

According to a student project for statistics 250, the amount of money spent on texts per semester by the population of students at a small liberal arts college is normally distributed with a mean of $426 and a standard deviation of $54. Determine the percent of all samples of...
*October 29, 2008 by Mary*

**Statistics**

Suppose that the fit to the simple linear regression of Y on X from 6 observations produces the following residuals: -3.3, 2.1, -4.0, -1.5, 5.1, 1.6. a) What is the estimate of sigma squared? b) What is the estimate of sigma? c) What are the degrees of freedom? Sigma = ...
*March 14, 2007 by MMK*

**Statistics**

A random sample of 80 students at a large school shows an average grade of 72 in Algebra with a standard deviation of 4. What is the standard error?
*November 24, 2012 by Pearl*

**statistics**

The average amount spent at a fast-food restaurant in California was $3.30, with a standard deviation of $.40. Yet in Georgia, the average amount spent at a fast-food restaurant was $3.25, with a standard deviation of $.10. What do these statistics tell you about fast-food ...
*March 25, 2013 by Donna*

**statistics**

A manufacturer knows that their items have a normally distributed length, with a mean of 7.3 inches, and standard deviation of 0.6 inches. If one item is chosen at random, what is the probability that it is less than 5.5 inches long?
*January 16, 2012 by Rhi*

**statistics**

For a normal distribution with a mean of 140 and a standard deviation of 55 find each value requested. a. What is the minimum score needed to be in the bottom 10% of the distribution? b. What scores form the boundaries for the middle 75% of the distribution.
*April 29, 2012 by tammy*

**Statistics**

Electricity bills in a certain city have mean $120.08. Assume the bills are normally distributed with standard deviation $14.40. Find the value that separates the lower 52% of the bills from the rest.
*June 16, 2013 by Anonymous*

**statistics**

The cutoff "t" needed is -1.8333. The standard deviation of the distribution of means of change scores is 2.0 and the mean change score for the sample studied is an increase of 5.2. What is the t score?
*November 4, 2009 by Brenda*

**Statistics**

bob received a z score of 0.9 on a college entrance exam. If the raw scores have a mean of 540 and a standard deviation of 80 points,what is his raw score?
*December 17, 2009 by Sarah*

**statistics**

Scores on a test have a mean of 66 and Q3 of 81. The scores have a distribution that is approximately normal. Find the standard deviation. Round your answer to the nearest tenth.
*March 29, 2010 by Abby*

**Statistics**

Assume the body temperature of healthy adults are normally distributed with a mean of 98.2 degrees F and a standard deviation of .62 degrees F. If you have a temperature of 99.0 what is your percentile score?
*November 16, 2010 by Lisa*

**statistics**

The average (arithmetic mean) of a normal distribution of a school's test scores is 65, and standard deviation of the distribution is 6.5. A student scoring a 78 on the exam is in what percentile of the school?
*December 24, 2010 by Anonymous*

**Statistics**

Suppose that heights of newborns are bell shaped with a mean of 6.8 pounds and a standard deviation of 1.3 pounds. What percentage of weights are: a) Below 6.8 lbs.? b) Above 8.3 lbs.?
*May 4, 2011 by Erik *

**Statistics**

Suppose that heights of newborns are bell shaped with a mean of 6.8 pounds and a standard deviation of 1.3 pounds. What percentage of weights are: a) Below 6.8 lbs.? b) Above 8.3 lbs.?
*May 6, 2011 by Erik *

**statistics-math**

The mean score on a Math exam was 50% and the standard deviation was 10%. Assume the results were normally distributed. (a) What percent of students earned a score between 50% and 70%? ( /2)
*November 9, 2011 by Noelle*

**Statistics**

The amount of a monthly phone bill is normally distributed with a mean of $60 and a standard deviation of $12. Fill in the blanks: 68% of her phone bills are between $______________ and $______________.
*July 23, 2012 by Adam*

**statistics**

A normal distribution has a mean of 36 and standard deviation of 4. What proportion of the distribution consisted of scores between x=34 and x=38? a, 0.6915 b, 2(0.3085)=0.6170 c, 0.1915 d, 2(0.1915)=0.3930
*November 9, 2012 by Robbie*

**statistics**

The average score on a science test was 72 with a standard deviation of 6. The average score on a history test was 89 with a standard deviation of 7. Compare the variability of the two classes.
*March 20, 2012 by Hannah*

**math**

One of the tallest living men has a height of 263 cm. One of the tallest living women is 245 cm tall. Heights of men have a mean of 177 cm and a standard deviation of 8 cm. Heights of women have a mean of 163 cm and a standard deviation of 4 cm. Relative to the population of ...
*February 13, 2015 by Liamz*

**statistics**

Jim Tree sells trees. The mean length of the trees purchased was 68 inches with a standard deviation of 10 inches. Jim wants to know what percent of his sales were more than 84 inches tall. He can use the standard normal distribution to help him. He asks, "what is the mean?" ...
*March 20, 2013 by Jessie*

**Statistics **

The Amount of filling a half-liter (500ml)soft drink bottle is normally distributed. The process has a standard deviation of 5ml. The mean is adjustable. A. Where should the mean be set to ensure a 95% probability that a half-liter bottle will not be under filled? B. A 99% ...
*April 11, 2014 by KT*

**math**

Suppose a test of musical ability has a normal distribution with a mean of 50 and a standard deviation of 5. Approximately what percentage of people are over 55? a. 6% b. 16% c. 45% d. 84% A z-score of 1.75 indicates how many standard deviation units above the mean? a. 1.75 b...
*May 8, 2010 by Amanda*

**Math please help!**

According to a student project for statistics 250, the amount of money spent on texts per semester by the population of students at a small liberal arts college is normally distributed with a mean of $426 and a standard deviation of $54. Determine the percent of all samples of...
*October 30, 2008 by Mary*

**statistics**

A pilot study has revealed a sample standard deviation of 16 for age of people in the work force. How large a sample must be chose to obtain an estimator of the mean that, with 95% confidence, will be correct to within 2 years?
*March 20, 2009 by Sally*

**Statistics**

Sample salaries (in dollars) of high school teachers are listed. Find the sample mean and standard deviation of the data. 49,632 54,619 58,298 48,250 51,842 50,875 43,219 49,924
*February 13, 2010 by bridget*

**statistics**

A large group of students has taken a college entrance exam. The scores on the exam are such that the mean = 52 and the standard deviation = 11 Find the probability that a student, selected at random, earned a score lower than 63.
*June 24, 2011 by MM*

**statistics**

If the mean value of the weight of a particular brand of dog food is 20.6 lb and the standard deviation is 1.3, assume a normal distribution and calculate the amount of product produced that falls below the lower specification value of 19.7 lb.
*February 9, 2012 by tonja*

**statistics**

The number of cell phone minutes used by high school seniors follows a normal distribution with a mean of 500 and a standard deviation of 50. What is the probability that a student uses more than 350 minutes?
*July 28, 2012 by Anonymous*

**statistics**

the mean scale score on the mathematics examination of ninth grade students in new york state was 86 with a standard deviation of 5 points. Given a student was selected at random what is the probabilty that his score was 91 or higher?
*February 9, 2013 by kelly*

**statistics**

Suppose that the test scores for a college entrance exam are normally distributed with a mean of 450 and a standard deviation of 100. If a student is selected at random what is the probability that the student will score above 600?
*April 24, 2013 by kevin*

**statistics**

A popular retail store knows that the purchase amounts by its customers is a random variable that follows a normal distribution with a mean of $30 and a standard deviation of $9. What is the probability that a randomly selected customer will spend between $20 and $35 at this ...
*September 24, 2013 by Selene*

**satistics**

3.Give the mean for the mean column of the Worksheet. Is this estimate centered about the parameter of interest (the parameter of interest is the answer for the mean in question 2)? Mean 3.50 Standard deviation 1.317 4.Give the mean for the median column of the Worksheet. Is ...
*December 4, 2011 by charlene*

**Statistics**

Scores on a visual perception test are normally distributed with a mean of 2020 and a standard deviation of 250. a)If one subject is randomly selected and tested, find the probability of a score greater than 1800 b)if 50 subjects are randomly selected and tested fid the ...
*March 21, 2013 by Sunshine*

**statistics**

Scores on a visual perception test are normally distributed with a mean of 2020 and a standard deviation of 250. a)If one subject is randomly selected and tested, find the probability of a score greater than 1800 b)if 50 subjects are randomly selected and tested fid the ...
*March 21, 2013 by Sunshine*

**math**

stat theory says approximately 68% of measurements lie between +- one standard deviation. assume we have 100 students in our class. if in midterm 1 the mean score is 80 and standard deviation is 6, and you scored 86. approximately how many students scored below you?
*September 16, 2013 by math standard deviation*

**statistics**

assume the body temperature of healthy adults distributed with a mean of 98.20F and a standard deviation of 0.62F. If you have a body temperature of 99.00F, what is your percentile score?
*May 16, 2010 by Christine*

**Statistics**

The heights of male students in a given university are normally distributed, with a mean of 70 inches and a standard deviation of .5 inches. Find the height (x value) that corresponds to the z value of -1.33.
*June 8, 2011 by Tony *

**Statistics**

The distribution of scores on a test is mound-shaped and symmetric with a mean score of 78. If 68% of the scores fall between 72 and 84, which of the following is most likely to be the standard deviation of the distribution? 3, 1, 4, 6?
*March 12, 2012 by MJ*

**statistics**

In a psychology class of 100 students, test scores are normally distributed with a mean of 80 and a standard deviation of 5. Approximately what percentage of students have scores between 70 and 90? A. 68% B. 80% C. 95% D. 99%
*August 15, 2012 by StudentD*

**statistics**

2. A test measuring basic math skills in adults is normally distributed, with mean = 20 and standard deviation = 7. Calculate the z score and T score for each of the following test scores: - X = 11
*December 12, 2012 by Angela*

**ELEMENTARY STATISTICS**

50 MATH PROFESSORS WERE ASKED HOW LONG IT TAKES TO GRADE A STUDENT'S HOMEWORK ASSIGNMENT. THE MEAN GRADING TIME FOR THE SAMPLE WAS 36.2 MINUTES WITH A STANDARD DEVIATION OF 4.8 MINUTES. WHAT IS THE 99% CONFIDENCE INTERVAL FOR THE MEAN GRADING TIME OF ALL MATH PROFESSORS?
*November 25, 2011 by DARLENE*

**statistics**

Suppose that the ages of students at a particular university average 26 years with a standard deviation of 2.8 years. Consider the sampling distribution of the sample mean age of students in a sample of n = 49. The mean of the sampling distribution is __________
*July 9, 2014 by Taylor*

**Statistics**

with a mean/median/mode value of 22 and a standard deviation of 17. Based on these numbers, we can say that approximately 50 percent of SOC 390 students work more than ____ hours per week? ..I don't understand how to figure this question out?
*November 7, 2011 by mary*

**statistics**

It is known that the population mean for the Full Scale IQ of the WAIS is 100 with a standard deviation of 15. A researcher assesses a sample of 200 adults and find that they have a mean Full Scale IQ of 102. The point estimate of the mean for this group is ___________ and the...
*April 15, 2014 by Katie*

**statistics**

The heights of 10000 individuals are approximately normally distributed with a mean of 70 inches and a standard deviation of 3 inches. Find the probability that a person picked at random from this group will be between 65 and 74 inches tall.
*October 27, 2010 by sohail*

**statistics**

The heights of 10000 individuals are approximately normally distributed with a mean of 70 inches and a standard deviation of 3 inches. Find the probability that a person picked at random from this group will be between 65 and 74 inches tall.
*October 27, 2010 by sohail*

**Statistics**

A particular fruit's weights are normally distributed, with a mean of 308 grams and a standard deviation of 31 grams. The heaviest 9% of fruits weigh more than how many grams? Give your answer to the nearest gram.
*April 12, 2011 by Sarah S-Help!*

**Statistics**

The distribution of heights of American women aged 18 to 24 is approximately normally distributed with mean 65.5 inches and standard deviation 2.5 inches. What is the probability that a randomly selected woman is over 70 inches tall?
*July 24, 2011 by Stacey Moore*

**statistics**

The lifetime of a 2- volt non- rechargeable battery in constant use has a normal distribution with a mean of 516 hours and a standard deviation of 20 hours. What is the z-score for batteries with lifetimes of 600 hours?
*September 6, 2012 by Gee*

**statistics**

The distribution of heights of American women aged 18 to 24 is approximately normally distributed with mean 65.5 inches and standard deviation 2.5 inches. What is the probability that a randomly selected woman is between 60 and 64 inches tall?
*May 8, 2013 by ali awan*

**Statistics**

The time to fly between New York City and Chicago is normally distributed with a mean of 180 minutes and a standard deviation of 17 minutes. What is the probability that a flight is more than 200 minutes?
*February 10, 2015 by Susan*

**statistic**

The Tite Wire Company manufactures wires for circus acts. It has taken a random sample of 100 pieces of wire and wants to see if the thickness of a batch of wire meets minimum specifications. Assume that the population mean is 0.45 inch, with a standard deviation of 0.03 inch...
*April 4, 2012 by Nancy*

**statistic**

The Tite Wire Company manufactures wires for circus acts. It has taken a random sample of 100 pieces of wire and wants to see if the thickness of a batch of wire meets minimum specifications. Assume that the population mean is 0.45 inch, with a standard deviation of 0.03 inch...
*April 7, 2012 by Nancy*

**Statistics**

In the library on a university campus, there is a sign in the elevator that indicates a limit of 16 people. in addition there is a weight limit of 2500 lbs. assume that the average weight of students, faculty, and staff on campus is 150 lbs, that the standard deviation is 27 ...
*June 2, 2013 by Eric*

**Statistics**

In the library on a university campus, there is a sign in the elevator that indicates a limit of 16 people. in addition there is a weight limit of 2500 lbs. assume that the average weight of students, faculty, and staff on campus is 150 lbs, that the standard deviation is 27 ...
*June 2, 2013 by Eric*

**Statistics**

A private medical clinic wants to estimate the true mean annual income of its patients. The clinic needs to be within $100 of the true mean. The clinic estimates that the true population standard deviation is around $2,100. If the confidence level is 95%, find the required ...
*April 15, 2012 by Jason*

**advanced algebra**

The mean test scores with standard deviations of four English classes are given below. Class Mean Standard Deviation Mrs. Jones 89 1.9 Mrs. Rijo 82 1.4 Mr. Phan 73 3.4 Mrs. Scott 90 6.1 Which statement is most likely to be true?
*September 22, 2014 by nautica*

**Statistics NEEED YOUR HELP ASAP!!!!!!!!!!!!!!**

The manufacturer of the X-15 steel-belted radial truch tire claims that the mean mileage the tire can be driven before the tread wears out is 80,000 km. The standard deviation of the mileage is 8,000 km. The Crosset Truck Company bought 48 tires and found that the mean mileage...
*April 3, 2010 by Samir*

**statistics**

At a large publishing company, the mean age of proofreaders is 36.2 years, and the standard deviation is 3.7 years. If a random sample of 15 proofreaders is selected, find the probability that the mean age of the proofreaders in the sample will be between 36 and 37.5 years....
*October 22, 2010 by Cindy*

**statistics**

The owner of a computer repair shop has determined that their daily revenue has mean $7200 and standard deviation $1200. The daily revenue totals for the next 30 days will be monitored. What is the probability that the mean daily revenue for the next 30 days will exceed $7000?
*November 8, 2011 by UG*

**statistics**

The number of cars sold annually by used car salespeople is normally distributed with a standard deviation of 18. A random sample of 310 salespeople was taken and the mean number of cars sold annually was found to be 71. Find the 94% confidence interval estimate of the ...
*May 9, 2012 by lupita*

**statistics**

Sign in Assume that the mean score on a certain aptitude test across the nation is 100, and that the standard deviation is 20 points. Find the probability that the mean aptitude test score for a randomly selected group of 150 8th graders is between 99.5 and 100.5. Sign in
*May 20, 2012 by m elissa*

**statistics**

The duration of time it takes General Motors to build a car is normally distributed with a mean of 31 hours and a standard deviation of 2 hours. a) What is the probability that a single car, selected at random, will take between 28 and 34 hours? b) What is the probability that...
*April 25, 2013 by kevin*

**Statistics**

18. The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 100 and a standard deviation of 15. Given a class with 25 students, what is the probability that the class' average IQ score is between 85 and 115? A) 0.0026 B) 0.4987 C) 3.00 D) 0.9974
*October 22, 2011 by Steph*

**statistics**

Science scores for HS seniors in the US are normally distributed with a mean of 77 and a standard deviation of 7. Students scoring in the top 4% are eligible for a special prize. What is the approximate cutoff score a student must get in order to recieve the prize?
*February 27, 2012 by taylor*

**statistics**

Science scores for HS seniors in the US are normally distributed with a mean of 77 and a standard deviation of 7. Students scoring in the top 4% are eligible for a special prize. What is the approximate cutoff score a student must get in order to recieve the prize?
*February 27, 2012 by taylor*

**statistics**

Suppose that SAT scores among U.S. college students are normally distributed with a mean of 450 and a standard deviation of 150. What is the probability that a randomly selected individual from this population has an SAT score at or below 600?
*March 27, 2012 by Chris*

**Statistics**

male heights are normaly distributed with a mean of 70 and a standard deviation of 2.8 inches. for two randomly selected guys, what's the probability that both of them are 67 inches or shorter? show calculations. Can someone please help me quickly with this question?
*November 8, 2012 by Heather*

**Statistics **

1200 high school freshman were randomly selected for a national survey. Among survey participants, the mean grade-point average was 2.8, and standard deviation was 0.6. What is the margin of error, assuming a 95% confidence level?
*February 27, 2015 by Isabel*

**statistics**

Given a distribution of scores with a mean of 26 and standard deviation of 6. assuming normality what percentage of the cases fall between 18 and 27, what percentage of the cases lie above score 18 and below 29
*April 16, 2010 by Anshika Srivastava*