Exam 6: Discrete Probability Distributions

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored less than 60?

Determine the z-score associated with an area of 0.4925 from the mean of a normal distribution to That negative z-score.

A sample of 500 evening students revealed that their annual incomes were normally distributed With a mean income of $50,000 and a standard deviation of $4,000. What is the income that Separates the top 5% from the lower 95% of the incomes?

Which of the following is NOT a characteristic of the normal probability distribution?

Two competitive brothers, who work in two different industries, were comparing their salaries. Because there is a difference of 4 years in their respective work experience, they decided to Compare, not their actual salaries, but to compare their salaries against their company averages to See who is doing better. The following gives the brothers salaries, companies mean, and standard Deviation for each company. What is the z-score of Andy's salary?

(i. About 95.5% percent of the area under the normal curve is within plus three and minus three Standard deviations of the mean. (ii. The normal distribution is a continuous probability distribution. (iii) In a standard normal distribution, µ = 0 and σ = 1.

Determine the z-score associated with an area of .1950 from the mean of a normal distribution to That positive z-score.

The upper and lower limits of a uniform probability distribution are

The mean amount of gasoline and services charged by Key Refining Company credit customers is $70 per month. The distribution of amounts spent is approximately normal with a standard deviation Of $10. What is the probability of selecting a credit card customer at random and finding the Customer charged between $70 and $83?

Past experience of a large manufacturing firm with administering a test to recent college graduates Who had applied for a job revealed that the mean test score was 500, and the standard deviation Was 50. The distribution of the test scores was normal. Based on this experience, management is Considering placing a person whose score is in the upper 6 percent of the distribution directly into a Responsible position. What is the lowest score a college graduate must earn to qualify for a Responsible position?

A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½ Ounces. (i. The probability that a loaf of bread is < 20 ounces is 0.0. (ii. The probability that a loaf of bread is > 21 ounces is 0.9772. (iii) The probability that a loaf of bread is < 24 ounces is 0.00.

A study of a company's practice regarding the payment of invoices revealed that on the average an Invoice was paid 20 days after it was received. The standard deviation equalled five days. Assuming that the distribution is normal, what percent of the invoices were paid within 15 days of Receipt?

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution, approximately how many scored greater than 65?

From past history, the scores on a statistics test are normally distributed with a mean of 70% and a Standard deviation of 5%. To earn a "C" on the test, a student must be in the top 25% of the class. What should a student score to receive a "C"?

An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life For a particular use before they failed is 19.0 hours. The distribution of the lives approximated a Normal distribution. The standard deviation of the distribution was 1.2 hours. About 95.44 percent of The batteries failed between what two values?

i. A z-score is the distance between a selected value (X) and the population mean (μ) divided by the Population standard deviation (σ). ii. The standard normal distribution is a special normal distribution with a mean of 0 and a standard Deviation of 1. iii. A computed z for X values to the right of the mean is negative.

The mean of a normally distributed group of weekly incomes of a large group of executives is $1,000 and the standard deviation is $100. What is the z-score for an income of $1,100?

i. The mean of a normal distribution is represented by σ. ii. When referring to the normal probability function, there is not just one of them; there is a "family" Of them. iii. Some normal probability distributions have equal arithmetic means, but their standard deviations May be different.

The seasonal output of a new experimental strain of pepper plants was carefully weighed. The Mean weight per plant is 15.0 pounds, and the standard deviation of the normally distributed Weights is 1.75 pounds. Of the 200 plants in the experiment, how many produced peppers weighing Between 13 and 16 pounds?

A loaf of bread is normally distributed with a mean of 22 ounces and a standard deviation of ½ Ounces. (i. The probability that a loaf of bread is between 20.75 and 23.25 ounces is 0.9876. (ii. The probability that a loaf of bread is > 21 ounces is 0.9772.