Explore BrainMass

Normal Distribution

Normal distribution and Standard Error of the Mean

5. A professor at a local university noted that the grades of her students were normally distributed with a mean of 73 and a standard deviation of 11. a. The professor has informed us that 7.93 percent of her students received grades of A. What is the minimum score needed to receive a grade of A? b. Students who made 57.93 or

Choosing C

Test Taking When taking a multiple choice test, the old adage comes to mind: 'When in doubt, Pick C'. It turns out that this is true in many cases. On a multiple choice test, with four solutions, the middle two choices tend to be the most correct answers. This presents a Gaussian (normal) distribution for the choices A,

Sampling Distribution, Mean and Standard Deviation

See attachment for better symbol representation. 1) A manufacturer of paper used for packaging requires a minimum strength of 20 pounds per square inch. To check on the quality of the paper, a random sample of 10 pieces of paper is selected each hour from the previous hour's production and a strength measurement is recorded

Engineering Stats

Assume that (X,Y) is a two-dimensional continuous random variable with pdf... a) Compute the probability that X + Y ? 1. Please see attached for full question.

7 Elementary Statistics Problems - dice probability and normal distribution

Problems must be worked out so that the average first year college student can understand them. 1. If a gambler rolls two dice and gets a sum of 10. he wins $10, and if he gets a sum of three, he wins$20. The cost to play is $5. What is the expectation of this game? 2. A recent study found that the average life expectan

Normal probability distribution..

Birth weights of babies born to full-term pregnancies follow roughly a normal distribution. At Meadowbrook Hospital, the mean weight of babies born to full-term pregnancies is 7 lbs with a standard deviation of 14 ounces (1 pound = 16 ounces). a. Dr. Watts has 4 deliveries (all for full-term pregnancies) coming up during the

Problems on sampling, hypothesis testing and confidence interval

1.Which of the following statements about the sampling distribution of the sample mean is incorrect? a. The sampling distribution of the sample mean is approximately normal whenever the sample size is sufficiently large (n>30). b. The sampling distribution of the sample mean is generated by repeatedly taking samples of size n

Probability: Standard Deviation, Exponential Distribution and Expected Values

(8) 1. A manufacturer of electronics products expects that 1% of units fail during the warranty period. A sample of 600 independent units is tracked for warranty performance. a) What is the expected number of failures during the warranty period? b) What is the probability that none fails during the warranty period? c) What is

Case Study using normal distribution

A company supplies pins in bulk to a customer. The company uses an automatic lathe to produce the pins. Due to many causes - vibration, temperature, wear and tear, and the like - the lengths of the pins made by the machine are normally distributed with a mean of 1.012 inches and a standard deviation of 0.018 inch. The custome

Stepwise significance testing format

The most important material reclaimed from beverage bottles is PET plastic. A serious impurity is aluminum, which later can clog the filters in extruders when the recycled material is used. The following are the amounts (in ppm by weight of aluminum) found in bihourly samples of PET recovered at the plant over roughly a two day

Binomial pdf

The number of days per year that it snows in an eastern Idaho town is normally distributed with a mean of 25 days and a standard deviation of 5.4 days. 1. What is the chance that it snows exactly 25 days?

Find percentiles from a given normal distribution

Your firm is attempting to reduce its cost of maintenance of customers by culling the least-productive of them. A census of sales records was undertaken and it was determined that the mean level of sale of all customers was $235,000 with a standard deviation of $15,000. (a) It is your desire to eliminate from your customer po


6.38 Obtain the z-score that has an area of .95 to its right. 6.40 Find the following z-scores a. z0.03 b. z0.005

Normal distribution

6.12 a. The area under the standard normal curve with parameters m = 64.4 and o= 2.4 that lies to the left of 61 is 0.0783. Use this information to estimate the percentage of female's students who are shorter than 61 inches. 6.14 According to the National Health and Nutrition Examination Survey, the serum (noncellular portio

Using Excel to make plots of Gaussian distribution

I am using Analytical Chemistry 7th edition By Skoog, West, Holler, and Crouch. please let me know if any additional info. is needed. There is a sample of the graph in the book Chapter 6 and 7. Using Excel, construct a spreadsheet to make two plots of a Gaussian distribution: 1. relative frequency vs deviation from the mean

Basic Statistics Problem (Normal Distribution; Mean; Standard Deviation)

I am having trouble with PART B of this problem. Here is the whole problem: Assume body temperatures are normally distributed with mean of 98.2 and a standard dev. of 0.62 Part A) Assuming a hospital defines a fever as 100 or over, determine the percentage of a normal healthy person considered to have a fever using Z tabl


Question 1 If a normal distribution of empirical scores is converted to a distribution of z scores: A. The new mean will be zero B. The new standard deviation will be one C. Both A and B D. Neither A and B. Question 2 Milquetoasts gracious statistics professor at Northwestern announced that he would drop th

Uniform distribution

1. X_1,X_2,...,X_n are independent and uniformly distributed on [0,1] a. standardize X_1+X_2+...+x_n b. Give mgf of THE STANDARDIZED (a) sum. 2. Suppose X is normal with mean u and variance sigma^2. P{u<= X <= u + 1.5 sigma}

Find the Critical Values and Determine the Appropriate Distribution

Do one of the following as appropriate: a) Find the critical value t (alpha/2) b) Find the critical value z (alpha/2) c) State that neither the normal nor the t distribution applies. Problem: 95%; n= 40; sigma is unknown; population appears to be skewed. (See attachment for complete question and symbols that did not come


How do I know which distribution to use for the following and when/where do tables apply?: Nonstandard Normal Binomial Normal Standard normal Central limit theorem a) Mean is 0, stand. dev. is 0 degrees C., find P between 0.05 and 1.50 b)Mean is 63.6 and s.d. is 2.5; Club had requirement that women must be 70 inch

Intro Stats New (multi choice)

A. n=17. Find P(t<-1.746) aa) .05 bb).95 cc).45 dd) 1.0 B. A random sample of 64 observations is observed from a population of SAT scores in 2001. Which of the following is a correct statement? aa) It is the distribution of the observed 64 SAT scores. bb) X-bar is approximately normal. cc) The mean of all possible x-bars is ave

Normal Distrubution

An airline wants to find out how long it takes for a travel agent to complete an airline ticket order from a computer terminal. Assume that the mean transaction time is 150 seconds. also assume that the population of transaction times has normal frequency curve. Find the probability that the 150 and 175 seconds to complete if s

Only for 103997

Only for above listed OTA. Last one for this semester. Thank you. Hope you're around mid- June through July. Have a great summer! Problem: In a stan. normal distribution, find the z-score that separates the top 20% area from the bottom 80%.

Only for OTA 103997

Only for above listed OTA Body Temperatures normally distributed with a mean of 98.2 and a stan. dev. of 0.62. if 100 people randomly selected find probablity their mean body temperature is between 98.15 and 98.5 degrees.

Only for OTA 103997, 103300, or 103866

Only for above listed OTA's Assume thermometer readings are normally distributed with a mean of 0 degree and a Standard deviant of 1.00 degree F. Find indicated probability where z is reading in degrees. P(z<1.645)

Estimated percentile rank

Tthe mean for a special distribution is 100 and the standard deviation is 15. What is the estimated percentile for an individual who had a score of 90 on this scale?

Questions from Textbook: Statistics for Management (7th Ed. ) Levin & Rubin

1). In a normal distribution with a standard deviation of 5.0, the probability that an observation selected at random exceeds 21 is 0.14 (14%). a). Find the mean of the distribution. b). Find the value of below which 4 percent of the values in the distribution lie. 2). The company's manager calculates that it requires